fix: calculate_age now handles PostgreSQL date objects

Problem: dob Spalte ist DATE (PostgreSQL) → Python bekommt datetime.date,
nicht String → strptime() schlägt fehl → age = "unbekannt"

Fix: Prüfe isinstance(dob, str) und handle beide Typen:
- String → strptime()
- date object → direkt verwenden

Jetzt funktioniert {{age}} Platzhalter korrekt.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/placeholder_resolver.py

@@ -225,16 +225,21 @@ def get_activity_summary(profile_id: str, days: int = 14) -> str:
         return f"{row['count']} Einheiten in {days} Tagen (Ø {avg_min} min/Einheit, {int(row['total_kcal'] or 0)} kcal gesamt)"
 
 
-def calculate_age(dob: Optional[str]) -> str:
-    """Calculate age from date of birth."""
+def calculate_age(dob) -> str:
+    """Calculate age from date of birth (accepts date object or string)."""
     if not dob:
         return "unbekannt"
     try:
-        birth = datetime.strptime(dob, '%Y-%m-%d')
-        today = datetime.now()
+        # Handle both datetime.date objects and strings
+        if isinstance(dob, str):
+            birth = datetime.strptime(dob, '%Y-%m-%d').date()
+        else:
+            birth = dob  # Already a date object from PostgreSQL
+
+        today = datetime.now().date()
         age = today.year - birth.year - ((today.month, today.day) < (birth.month, birth.day))
         return str(age)
-    except:
+    except Exception as e:
         return "unbekannt"