Add DTOs for owner

backend/app/dtos/owner_detail_response.py

@@ -0,0 +1,7 @@
+from pydantic import BaseModel
+
+class OwnerDetailResponse(BaseModel):
+    id: str
+    user_id: str
+    email: str
+

backend/app/dtos/owner_list_response.py

@@ -0,0 +1,9 @@
+from pydantic import BaseModel
+
+class OwnerResponse(BaseModel):
+    id: str
+    user_id: str
+
+
+class OwnerListResponse(BaseModel):
+    owners: list[OwnerResponse]