fix: update sleep debt chart payload to ensure accurate date handling and current debt representation

- Modified the `build_sleep_debt_chart_payload` function to correctly handle date types, ensuring only valid dates are processed.
- Enhanced the logic to append today's date and current debt value to the chart data if the last recorded date is earlier than today, aligning the chart with KPI metrics.
- Updated metadata calculations to reflect the correct number of data points based on labels, improving the accuracy of the recovery chart payload.

backend/data_layer/recovery_chart_payloads.py

@@ -6,7 +6,7 @@ Ausgelagert aus routers/charts.py (Issue 53 / Layer 1).
 
 from __future__ import annotations
 
-from datetime import datetime, timedelta
+from datetime import date, datetime, timedelta
 from typing import Any, Dict, Optional, Set
 
 from db import get_db, get_cursor
@@ -333,14 +333,31 @@ def build_sleep_debt_chart_payload(profile_id: str, days: int) -> Dict[str, Any]
             },
         }
 
-    labels = []
-    debt_values = []
+    labels: list[str] = []
+    debt_values: list[float] = []
     for r in visible:
         rd = r.get("date")
         end_d = rd.date() if isinstance(rd, datetime) else rd
-        labels.append(end_d.isoformat() if hasattr(end_d, "isoformat") else str(end_d))
+        if not isinstance(end_d, date):
+            continue
+        labels.append(end_d.isoformat())
         debt_values.append(sleep_debt_sum_hours_in_window(all_rows, end_d))
 
+    # KPI nutzt immer Fensterende = heute; die Kurve endete bisher am Datum der letzten Schlaf-Zeile
+    # (z. B. gestern) → anderes 14-Tage-Fenster. Letzter Punkt = exakt KPI-Wert, Datum = heute.
+    today = datetime.now().date()
+    if labels and debt_values:
+        try:
+            last_d = date.fromisoformat(labels[-1])
+        except (TypeError, ValueError):
+            last_d = None
+        if last_d is not None:
+            if last_d < today:
+                labels.append(today.isoformat())
+                debt_values.append(float(current_debt))
+            elif last_d == today:
+                debt_values[-1] = float(current_debt)
+
     return {
         "chart_type": "line",
         "data": {
@@ -360,13 +377,14 @@ def build_sleep_debt_chart_payload(profile_id: str, days: int) -> Dict[str, Any]
         "metadata": serialize_dates(
             {
                 "confidence": calculate_confidence(len(visible), days, "general"),
-                "data_points": len(visible),
+                "data_points": len(labels),
                 "current_debt_hours": round(float(current_debt), 1),
                 "sleep_debt_target_hours_per_night": SLEEP_DEBT_TARGET_HOURS_DEFAULT,
                 "rolling_window_days": SLEEP_DEBT_ROLLING_WINDOW_DAYS,
                 "note": "Gleiche Formel wie KPI: Summe der nächtlichen Defizite vs. "
-                f"{SLEEP_DEBT_TARGET_HOURS_DEFAULT} h/Nacht im rollierenden {SLEEP_DEBT_ROLLING_WINDOW_DAYS}-Tage-Fenster "
-                "(jeder Punkt = Fensterende an dem Datum). Ziel aktuell nicht in den Profileinstellungen änderbar.",
+                f"{SLEEP_DEBT_TARGET_HOURS_DEFAULT} h/Nacht im rollierenden {SLEEP_DEBT_ROLLING_WINDOW_DAYS}-Tage-Fenster. "
+                "Zwischenpunkte: Fensterende = Datum der jeweiligen Schlaf-Zeile; "
+                "letzter Punkt ist auf «heute» bzw. KPI-Wert gesetzt, damit Kurve und Kachel übereinstimmen.",
             }
         ),
     }