feat: Implement focus area usage types management in API and UI

- Added endpoints for listing and updating focus area usage types in the backend.
- Enhanced the AdminFocusAreasPage to display and manage allowed usage types for focus areas.
- Introduced a new state for usage types catalog and integrated it into the focus area editing process.
- Updated API utility functions to support new usage types operations.

backend/focus_area_usage_helpers.py

@@ -0,0 +1,20 @@
+"""Kleine Helfer für Focus-Area-Nutzungstypen (ohne Router-/Auth-Abhängigkeiten)."""
+from __future__ import annotations
+
+import json
+from typing import Any, List
+
+
+def coerce_usage_type_keys(raw: Any) -> List[str]:
+    """json_agg / JSON-Spalte zu list[str] normalisieren."""
+    if raw is None:
+        return []
+    if isinstance(raw, list):
+        return [str(x) for x in raw]
+    if isinstance(raw, str):
+        try:
+            data = json.loads(raw)
+            return [str(x) for x in data] if isinstance(data, list) else []
+        except json.JSONDecodeError:
+            return []
+    return []

backend/migrations/036_focus_area_usage_types.sql

@@ -0,0 +1,36 @@
+-- Migration 036: Focus Area — erlaubte Nutzungstypen (Referenz + M:N)
+-- Date: 2026-04-06
+-- Purpose: System-seeded usage types; optional Zuordnung pro Focus Area (kein Auto-Backfill)
+
+-- Referenztabelle: feste, systemdefinierte Nutzungstypen
+CREATE TABLE IF NOT EXISTS focus_area_usage_types (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    key VARCHAR(64) UNIQUE NOT NULL,
+    label_de VARCHAR(160),
+    sort_order INT NOT NULL DEFAULT 0,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
+);
+
+COMMENT ON TABLE focus_area_usage_types IS
+    'Systemdefinierte Nutzungsarten für Focus Areas (kein Admin-CRUD in v1)';
+
+-- M:N: welche Nutzungstypen für eine Focus Area erlaubt sind (leer = noch nicht klassifiziert)
+CREATE TABLE IF NOT EXISTS focus_area_definition_usage_types (
+    focus_area_id UUID NOT NULL REFERENCES focus_area_definitions(id) ON DELETE CASCADE,
+    usage_type_id UUID NOT NULL REFERENCES focus_area_usage_types(id) ON DELETE CASCADE,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    PRIMARY KEY (focus_area_id, usage_type_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_fadut_focus_area ON focus_area_definition_usage_types(focus_area_id);
+CREATE INDEX IF NOT EXISTS idx_fadut_usage_type ON focus_area_definition_usage_types(usage_type_id);
+
+COMMENT ON TABLE focus_area_definition_usage_types IS
+    'Zuordnung Focus Area → erlaubte Nutzungstypen (kein automatisches Befüllen bestehender Areas)';
+
+-- Seed: nur die drei Typen — keine Zeilen in der Junction-Tabelle
+INSERT INTO focus_area_usage_types (key, label_de, sort_order) VALUES
+    ('goal_priority', 'Ziele / Prioritäten', 1),
+    ('expected_training_effect', 'Erwartetes Trainingseffekt-Profil', 2),
+    ('concrete_training_contribution', 'Konkrete Trainings-Beiträge / Belastungsausprägung', 3)
+ON CONFLICT (key) DO NOTHING;

backend/routers/focus_areas.py

@@ -3,10 +3,11 @@ Focus Areas Router
 Manages dynamic focus area definitions and user preferences
 """
 from fastapi import APIRouter, HTTPException, Depends
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 from typing import Optional, List
 from db import get_db, get_cursor, r2d
 from auth import require_auth
+from focus_area_usage_helpers import coerce_usage_type_keys
 
 router = APIRouter(prefix="/api/focus-areas", tags=["focus-areas"])
 
@@ -36,6 +37,11 @@ class UserFocusPreferences(BaseModel):
     """User's focus area weightings (dynamic)"""
     preferences: dict  # {focus_area_id: weight_pct}
 
+
+class FocusAreaUsageTypesUpdate(BaseModel):
+    """Replace all usage-type assignments for one focus area (admin)."""
+    usage_type_keys: List[str] = Field(default_factory=list)
+
 # ============================================================================
 # Focus Area Definitions (Admin)
 # ============================================================================
@@ -58,14 +64,27 @@ def list_focus_area_definitions(
 
         query = """
             SELECT id, key, name_de, name_en, icon, description, category, is_active,
-                   created_at, updated_at
+                   created_at, updated_at,
+                   COALESCE(
+                       (
+                           SELECT json_agg(faut.key ORDER BY faut.sort_order, faut.key)
+                           FROM focus_area_definition_usage_types fadut
+                           JOIN focus_area_usage_types faut ON faut.id = fadut.usage_type_id
+                           WHERE fadut.focus_area_id = focus_area_definitions.id
+                       ),
+                       '[]'::json
+                   ) AS allowed_usage_type_keys
             FROM focus_area_definitions
             WHERE is_active = true OR %s
             ORDER BY category, name_de
         """
 
         cur.execute(query, (include_inactive,))
-        areas = [r2d(row) for row in cur.fetchall()]
+        areas = []
+        for row in cur.fetchall():
+            d = r2d(row)
+            d['allowed_usage_type_keys'] = coerce_usage_type_keys(d.get('allowed_usage_type_keys'))
+            areas.append(d)
 
         # Group by category
         grouped = {}
@@ -75,6 +94,10 @@ def list_focus_area_definitions(
                 grouped[cat] = []
             grouped[cat].append(area)
 
+        if session.get('role') != 'admin':
+            for area in areas:
+                area.pop('allowed_usage_type_keys', None)
+
         return {
             "areas": areas,
             "grouped": grouped,
@@ -226,6 +249,92 @@ def delete_focus_area_definition(
 
         return {"message": "Focus Area gelöscht"}
 
+
+@router.get("/usage-types")
+def list_focus_area_usage_types(session: dict = Depends(require_auth)):
+    """
+    Liste aller systemdefinierten Nutzungstypen (Admin, Konfigurations-UI).
+    Keine freie Anlage neuer Typen über die API.
+    """
+    if session.get('role') != 'admin':
+        raise HTTPException(status_code=403, detail="Admin-Rechte erforderlich")
+
+    with get_db() as conn:
+        cur = get_cursor(conn)
+        cur.execute("""
+            SELECT id, key, label_de, sort_order
+            FROM focus_area_usage_types
+            ORDER BY sort_order, key
+        """)
+        rows = [r2d(r) for r in cur.fetchall()]
+        return {"usage_types": rows, "total": len(rows)}
+
+
+@router.put("/definitions/{area_id}/usage-types")
+def replace_focus_area_usage_types(
+    area_id: str,
+    data: FocusAreaUsageTypesUpdate,
+    session: dict = Depends(require_auth),
+):
+    """
+    Ersetzt die Nutzungstyp-Zuweisungen einer Focus Area (Admin).
+    Leere Liste entfernt alle Zuordnungen. Unbekannte Keys → 400.
+    """
+    if session.get('role') != 'admin':
+        raise HTTPException(status_code=403, detail="Admin-Rechte erforderlich")
+
+    keys = list(dict.fromkeys(data.usage_type_keys))  # dedupe, preserve order
+
+    with get_db() as conn:
+        cur = get_cursor(conn)
+
+        cur.execute(
+            "SELECT id FROM focus_area_definitions WHERE id = %s",
+            (area_id,),
+        )
+        if not cur.fetchone():
+            raise HTTPException(status_code=404, detail="Focus Area nicht gefunden")
+
+        if not keys:
+            cur.execute(
+                "DELETE FROM focus_area_definition_usage_types WHERE focus_area_id = %s",
+                (area_id,),
+            )
+            return {"message": "Nutzungstyp-Zuweisungen entfernt", "usage_type_keys": []}
+
+        placeholders = ','.join(['%s'] * len(keys))
+        cur.execute(
+            f"""
+            SELECT id, key FROM focus_area_usage_types
+            WHERE key IN ({placeholders})
+            """,
+            keys,
+        )
+        found = {row['key']: row['id'] for row in cur.fetchall()}
+        missing = [k for k in keys if k not in found]
+        if missing:
+            raise HTTPException(
+                status_code=400,
+                detail=f"Unbekannte Nutzungstyp-Keys: {', '.join(missing)}",
+            )
+
+        cur.execute(
+            "DELETE FROM focus_area_definition_usage_types WHERE focus_area_id = %s",
+            (area_id,),
+        )
+        for k in keys:
+            ut_id = found[k]
+            cur.execute(
+                """
+                INSERT INTO focus_area_definition_usage_types (focus_area_id, usage_type_id)
+                VALUES (%s, %s)
+                ON CONFLICT (focus_area_id, usage_type_id) DO NOTHING
+                """,
+                (area_id, ut_id),
+            )
+
+        return {"message": "Nutzungstyp-Zuweisungen aktualisiert", "usage_type_keys": keys}
+
 # ============================================================================
 # User Focus Preferences
 # ============================================================================

backend/tests/test_focus_area_usage_types.py

@@ -0,0 +1,127 @@
+"""
+Tests: Focus Area Nutzungstypen (Migration 036, Router-Helfer).
+
+Ohne MITAI_INTEGRATION_DB=1 werden nur SQL-Datei und reine Python-Helfer geprüft.
+Mit gesetztem Flag optional Verifikation gegen eine PostgreSQL-Instanz (Migration 036 angewendet).
+"""
+from __future__ import annotations
+
+import os
+import sys
+import uuid
+from pathlib import Path
+
+import pytest
+
+BACKEND_ROOT = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(BACKEND_ROOT))
+
+
+def test_migration_036_defines_schema_and_seeds_keys():
+    p = BACKEND_ROOT / "migrations" / "036_focus_area_usage_types.sql"
+    assert p.is_file(), f"expected {p}"
+    text = p.read_text(encoding="utf-8")
+    assert "CREATE TABLE IF NOT EXISTS focus_area_usage_types" in text
+    assert "CREATE TABLE IF NOT EXISTS focus_area_definition_usage_types" in text
+    for key in (
+        "goal_priority",
+        "expected_training_effect",
+        "concrete_training_contribution",
+    ):
+        assert key in text
+    assert "ON CONFLICT (key) DO NOTHING" in text
+    # Explizit: kein automatisches Befüllen der M:N-Tabelle
+    assert "INSERT INTO focus_area_definition_usage_types" not in text
+
+
+def test_coerce_usage_type_keys_normalizes_values():
+    from focus_area_usage_helpers import coerce_usage_type_keys
+
+    assert coerce_usage_type_keys(None) == []
+    assert coerce_usage_type_keys([]) == []
+    assert coerce_usage_type_keys(["goal_priority", "expected_training_effect"]) == [
+        "goal_priority",
+        "expected_training_effect",
+    ]
+    assert coerce_usage_type_keys('["concrete_training_contribution"]') == [
+        "concrete_training_contribution"
+    ]
+
+
+@pytest.mark.skipif(
+    os.getenv("MITAI_INTEGRATION_DB") != "1",
+    reason="Set MITAI_INTEGRATION_DB=1 plus DB_* env to run DB checks (nur Dev/CI!)",
+)
+def test_integration_focus_area_usage_types_seeded_and_junction_writable():
+    """Nur gegen Dev-DB ausführen. Nutzt temporäre focus_area_definitions-Zeile, keine bestehenden Daten."""
+    from db import get_db, get_cursor
+    from focus_area_usage_helpers import coerce_usage_type_keys
+
+    tmp_id = str(uuid.uuid4())
+    tmp_key = f"tmp_usage_{tmp_id[:8]}"
+
+    with get_db() as conn:
+        cur = get_cursor(conn)
+        cur.execute(
+            """
+            SELECT key FROM focus_area_usage_types
+            ORDER BY sort_order, key
+            """
+        )
+        keys = [row["key"] for row in cur.fetchall()]
+        assert keys == [
+            "goal_priority",
+            "expected_training_effect",
+            "concrete_training_contribution",
+        ]
+
+        cur.execute(
+            """
+            INSERT INTO focus_area_definitions
+            (id, key, name_de, category, is_active)
+            VALUES (%s, %s, 'tmp_test_usage', 'custom', false)
+            """,
+            (tmp_id, tmp_key),
+        )
+
+        cur.execute(
+            """
+            SELECT COALESCE(
+                (
+                    SELECT json_agg(faut.key ORDER BY faut.sort_order, faut.key)
+                    FROM focus_area_definition_usage_types fadut
+                    JOIN focus_area_usage_types faut ON faut.id = fadut.usage_type_id
+                    WHERE fadut.focus_area_id = %s
+                ),
+                '[]'::json
+            ) AS allowed_usage_type_keys
+            """,
+            (tmp_id,),
+        )
+        assert coerce_usage_type_keys(cur.fetchone()["allowed_usage_type_keys"]) == []
+
+        cur.execute(
+            """
+            INSERT INTO focus_area_definition_usage_types (focus_area_id, usage_type_id)
+            SELECT %s, u.id FROM focus_area_usage_types u WHERE u.key = %s
+            """,
+            (tmp_id, "goal_priority"),
+        )
+        cur.execute(
+            """
+            INSERT INTO focus_area_definition_usage_types (focus_area_id, usage_type_id)
+            SELECT %s, u.id FROM focus_area_usage_types u WHERE u.key = %s
+            """,
+            (tmp_id, "expected_training_effect"),
+        )
+        cur.execute(
+            """
+            SELECT COUNT(*) AS n
+            FROM focus_area_definition_usage_types
+            WHERE focus_area_id = %s
+            """,
+            (tmp_id,),
+        )
+        assert cur.fetchone()["n"] == 2
+
+        cur.execute("DELETE FROM focus_area_definitions WHERE id = %s", (tmp_id,))

frontend/src/pages/AdminFocusAreasPage.jsx

@@ -14,8 +14,19 @@ const CATEGORIES = [
   { value: 'custom', label: 'Eigene' }
 ]
 
+function groupAreasByCategory(areas) {
+  const grouped = {}
+  for (const area of areas) {
+    const cat = area.category || 'other'
+    if (!grouped[cat]) grouped[cat] = []
+    grouped[cat].push(area)
+  }
+  return grouped
+}
+
 export default function AdminFocusAreasPage() {
   const [data, setData] = useState({ areas: [], grouped: {}, total: 0 })
+  const [usageTypesCatalog, setUsageTypesCatalog] = useState([])
   const [loading, setLoading] = useState(true)
   const [error, setError] = useState(null)
   const [showInactive, setShowInactive] = useState(false)
@@ -34,11 +45,35 @@ export default function AdminFocusAreasPage() {
     loadData()
   }, [showInactive])
 
+  useEffect(() => {
+    let cancelled = false
+    ;(async () => {
+      try {
+        const r = await api.listFocusAreaUsageTypes()
+        if (!cancelled) setUsageTypesCatalog(r.usage_types || [])
+      } catch (e) {
+        console.error('usage-types catalog:', e)
+        if (!cancelled) setUsageTypesCatalog([])
+      }
+    })()
+    return () => { cancelled = true }
+  }, [])
+
   const loadData = async () => {
     try {
       setLoading(true)
       const result = await api.listFocusAreaDefinitions(showInactive)
-      setData(result)
+      const areas = (result.areas || []).map(a => ({
+        ...a,
+        allowed_usage_type_keys: Array.isArray(a.allowed_usage_type_keys)
+          ? a.allowed_usage_type_keys
+          : []
+      }))
+      setData({
+        areas,
+        grouped: groupAreasByCategory(areas),
+        total: result.total ?? areas.length
+      })
       setError(null)
     } catch (err) {
       console.error('Failed to load focus areas:', err)
@@ -74,14 +109,20 @@ export default function AdminFocusAreasPage() {
   const handleUpdate = async (id) => {
     try {
       const area = data.areas.find(a => a.id === id)
-      await api.updateFocusAreaDefinition(id, {
-        name_de: area.name_de,
-        name_en: area.name_en,
-        icon: area.icon,
-        description: area.description,
-        category: area.category,
-        is_active: area.is_active
-      })
+      const usageKeys = Array.isArray(area.allowed_usage_type_keys)
+        ? area.allowed_usage_type_keys
+        : []
+      await Promise.all([
+        api.updateFocusAreaDefinition(id, {
+          name_de: area.name_de,
+          name_en: area.name_en,
+          icon: area.icon,
+          description: area.description,
+          category: area.category,
+          is_active: area.is_active
+        }),
+        api.setFocusAreaUsageTypes(id, usageKeys)
+      ])
       setEditingId(null)
       await loadData()
     } catch (err) {
@@ -113,12 +154,25 @@ export default function AdminFocusAreasPage() {
   }
 
   const updateField = (id, field, value) => {
-    setData(prev => ({
-      ...prev,
-      areas: prev.areas.map(a =>
+    setData(prev => {
+      const areas = prev.areas.map(a =>
         a.id === id ? { ...a, [field]: value } : a
       )
-    }))
+      return { ...prev, areas, grouped: groupAreasByCategory(areas), total: areas.length }
+    })
+  }
+
+  const toggleUsageTypeKey = (areaId, key, checked) => {
+    setData(prev => {
+      const areas = prev.areas.map(a => {
+        if (a.id !== areaId) return a
+        const cur = new Set(Array.isArray(a.allowed_usage_type_keys) ? a.allowed_usage_type_keys : [])
+        if (checked) cur.add(key)
+        else cur.delete(key)
+        return { ...a, allowed_usage_type_keys: [...cur] }
+      })
+      return { ...prev, areas, grouped: groupAreasByCategory(areas), total: areas.length }
+    })
   }
 
   if (loading) {
@@ -364,6 +418,45 @@ export default function AdminFocusAreasPage() {
                         />
                       </div>
 
+                      <div>
+                        <label style={{ fontSize: 12, fontWeight: 600, display: 'block', marginBottom: 6 }}>
+                          Erlaubte Nutzungstypen
+                        </label>
+                        {usageTypesCatalog.length === 0 ? (
+                          <span style={{ fontSize: 12, color: 'var(--text3)' }}>
+                            Kein Katalog geladen (Backend / Migration prüfen).
+                          </span>
+                        ) : (
+                          <div style={{ display: 'flex', flexDirection: 'column', gap: 8 }}>
+                            {usageTypesCatalog.map(ut => (
+                              <label
+                                key={ut.id}
+                                style={{
+                                  fontSize: 13,
+                                  display: 'flex',
+                                  alignItems: 'flex-start',
+                                  gap: 8,
+                                  cursor: 'pointer'
+                                }}
+                              >
+                                <input
+                                  type="checkbox"
+                                  style={{ marginTop: 3 }}
+                                  checked={(area.allowed_usage_type_keys || []).includes(ut.key)}
+                                  onChange={(e) =>
+                                    toggleUsageTypeKey(area.id, ut.key, e.target.checked)
+                                  }
+                                />
+                                <span>
+                                  <span style={{ display: 'block' }}>{ut.label_de}</span>
+                                  <code style={{ fontSize: 11, color: 'var(--text3)' }}>{ut.key}</code>
+                                </span>
+                              </label>
+                            ))}
+                          </div>
+                        )}
+                      </div>
+
                       <div style={{ display: 'flex', gap: 8 }}>
                         <button
                           className="btn-primary"
@@ -430,6 +523,37 @@ export default function AdminFocusAreasPage() {
                             {area.description}
                           </div>
                         )}
+
+                        {(area.allowed_usage_type_keys || []).length > 0 && (
+                          <div
+                            style={{
+                              fontSize: 12,
+                              marginTop: 8,
+                              display: 'flex',
+                              flexWrap: 'wrap',
+                              gap: 6
+                            }}
+                          >
+                            {(area.allowed_usage_type_keys || []).map(k => {
+                              const ut = usageTypesCatalog.find(x => x.key === k)
+                              return (
+                                <span
+                                  key={k}
+                                  style={{
+                                    padding: '2px 8px',
+                                    borderRadius: 6,
+                                    background: 'var(--surface2)',
+                                    border: '1px solid var(--border)',
+                                    color: 'var(--text2)'
+                                  }}
+                                  title={k}
+                                >
+                                  {ut?.label_de || k}
+                                </span>
+                              )
+                            })}
+                          </div>
+                        )}
                       </div>
 
                       <div style={{ display: 'flex', gap: 6, flexShrink: 0 }}>

frontend/src/utils/api.js

@@ -375,6 +375,9 @@ export const api = {
   getUserFocusPreferences:   ()   => req('/focus-areas/user-preferences'),
   updateUserFocusPreferences: (d) => req('/focus-areas/user-preferences', jput(d)),
   getFocusAreaStats:         ()   => req('/focus-areas/stats'),
+  listFocusAreaUsageTypes:   ()   => req('/focus-areas/usage-types'),
+  setFocusAreaUsageTypes:    (id, usageTypeKeys) =>
+    req(`/focus-areas/definitions/${id}/usage-types`, jput({ usage_type_keys: usageTypeKeys })),
 
   // Chart Endpoints (Phase 0c - Phase 1: Nutrition + Recovery)
   // Nutrition Charts (E1-E5)