fix(csv_parser): Normalize header comparison in CSV template validation

- Updated the `validate_csv_template` function to normalize both the column signature and field mappings for accurate comparison, preventing false warnings about mismatches.
- Enhanced warning messages to provide clearer guidance on the relationship between normalized signatures and raw field mappings.
- Added a new test to ensure that normalized signatures do not trigger false warnings when compared to raw mappings.

backend/csv_parser/template_validator.py

@@ -8,6 +8,7 @@ from __future__ import annotations
 
 from typing import Any, Mapping
 
+from csv_parser.core import normalize_header_for_signature
 from csv_parser.import_row_processing import validate_import_row_processing as validate_import_row_processing_spec
 from csv_parser.module_registry import (
     get_module_definition,
@@ -206,17 +207,28 @@ def validate_csv_template(
                     )
                 )
 
-    # Signatur vs. gemappte Spalten (nur Hinweis)
+    # Signatur vs. gemappte Spalten: beide Seiten wie beim Import normalisieren
+    # (column_signature kann sortierte Normalform aus Analyse sein, field_mappings rohe Header).
     if column_signature:
-        sig_norm = {str(c).strip() for c in column_signature if str(c).strip()}
+        sig_forms = {
-        mapped_cols = {str(k).strip() for k in fm.keys()}
+            normalize_header_for_signature(str(c))
-        if sig_norm and not sig_norm.intersection(mapped_cols):
+            for c in column_signature
+            if str(c).strip()
+        }
+        sig_forms.discard("")
+        mapped_forms = {
+            normalize_header_for_signature(str(k))
+            for k in fm.keys()
+            if str(k).strip()
+        }
+        mapped_forms.discard("")
+        if sig_forms and mapped_forms and not sig_forms.intersection(mapped_forms):
             warnings.append(
                 _issue(
                     "warning",
                     "signature_vs_mappings_mismatch",
-                    "column_signature und die Schlüssel in field_mappings haben keine gemeinsame Spalte.",
+                    "column_signature und field_mappings (Schlüssel) haben nach Normalisierung keine gemeinsame Spalte.",
-                    hint="Signatur dient dem Ranking; für den Import müssen die Kopfzeilen der Datei zu den Keys in field_mappings passen (oder Aliase greifen).",
+                    hint="Prüfen Sie, ob die gespeicherte Signatur zur CSV passt; Zuordnungen nutzen rohe Kopfzeilen, die Signatur oft die gleiche Normalform wie in der Analyse.",
                 )
             )
 

backend/tests/test_template_validator.py

@@ -30,6 +30,31 @@ def test_validate_invalid_target_error():
     assert any(e["code"] == "invalid_field_mapping" for e in r["errors"])
 
 
+def test_signature_normalized_vs_raw_mapping_no_false_warning():
+    """Analyse liefert normalisierte Signatur; field_mappings nutzt Original-Header wie im Seed."""
+    r = validate_csv_template(
+        "blood_pressure",
+        {
+            "Datum": "measured_date",
+            "Zeit": "measured_time",
+            "Systolisch (mmHg)": "systolic",
+            "Diastolisch (mmHg)": "diastolic",
+            "Puls (bpm)": "pulse",
+        },
+        {
+            "measured_date": {"type": "date", "format": "dd.mm.yyyy"},
+            "measured_time": {"type": "time", "format": "HH:MM"},
+            "systolic": {"type": "int"},
+            "diastolic": {"type": "int"},
+            "pulse": {"type": "int"},
+        },
+        None,
+        ["datum", "diastolisch_mmhg", "puls_bpm", "systolisch_mmhg", "zeit"],
+    )
+    assert r["valid"] is True
+    assert not any(w["code"] == "signature_vs_mappings_mismatch" for w in r["warnings"])
+
+
 def test_validate_duplicate_target_warning():
     r = validate_csv_template(
         "weight",