Harden RC7 API response contracts

backend/app/services/area_service.py

@@ -15,9 +15,19 @@ from app.utils.geometry import area_m2, geometry_bbox_polygon, normalize_to_mult
 class AreaService:
     @staticmethod
     def serialize_area(area: Area) -> dict:
-        payload = AreaRead.model_validate(area).model_dump()
-        payload["geometry"] = mapping(to_shape(area.geometry)) if area.geometry else None
-        return payload
+        geometry = to_shape(area.geometry) if area.geometry else None
+        return AreaRead.model_validate(
+            {
+                "id": area.id,
+                "project_id": area.project_id,
+                "name": area.name,
+                "original_crs": area.original_crs,
+                "area_m2": area.area_m2,
+                "created_at": area.created_at,
+                "geometry_type": geometry.geom_type if geometry else None,
+                "geometry": mapping(geometry) if geometry else None,
+            }
+        ).model_dump()
 
     @staticmethod
     def list_areas(db: Session, project_id: uuid.UUID, limit: int = 50, offset: int = 0) -> tuple[list[Area], int]: