fix: convert Decimal to float before multiplication in protein targets

- get_protein_ziel_low: float(weight) * 1.6
- get_protein_ziel_high: float(weight) * 2.2

Fixes TypeError: unsupported operand type(s) for *: 'decimal.Decimal' and 'float'

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

backend/placeholder_resolver.py

@@ -184,7 +184,7 @@ def get_protein_ziel_low(profile_id: str) -> str:
         )
         row = cur.fetchone()
         if row:
-            return f"{int(row['weight'] * 1.6)}"
+            return f"{int(float(row['weight']) * 1.6)}"
         return "nicht verfügbar"
 
 
@@ -199,7 +199,7 @@ def get_protein_ziel_high(profile_id: str) -> str:
         )
         row = cur.fetchone()
         if row:
-            return f"{int(row['weight'] * 2.2)}"
+            return f"{int(float(row['weight']) * 2.2)}"
         return "nicht verfügbar"