raise ValueError for bool inputs instead of returning as-is

Agent-Logs-Url: https://github.com/dylanlangston/nextcloud-mcp-server/sessions/0360ab28-8913-450e-8c61-697e71ba9742

Co-authored-by: dylanlangston <16236219+dylanlangston@users.noreply.github.com>

nextcloud_mcp_server/models/cookbook.py

@@ -64,7 +64,8 @@ class Nutrition(BaseModel):
         stores whatever the source provided.
         """
         if isinstance(v, bool):
-            return v
+            msg = "boolean values are not valid for nutrition fields"
+            raise ValueError(msg)
         if isinstance(v, (int, float)):
             return str(v)
         return v