refactor: 重构 schemas 结构，统一枚举定义

backend/tests/integration/test_friendship_routes.py

@@ -9,7 +9,7 @@ from fastapi.testclient import TestClient
 
 from app import app
 from core.auth.models import CurrentUser
-from schemas.user.context import UserContext
+from schemas.shared.user import UserContext
 from v1.friendships.dependencies import get_friendship_service
 from v1.friendships.schemas import (
     FriendRequestCreate,

backend/tests/integration/test_users_routes.py

@@ -8,7 +8,7 @@ from fastapi.testclient import TestClient
 
 from app import app
 from core.auth.models import CurrentUser
-from schemas.user.context import UserContext
+from schemas.shared.user import UserContext
 from v1.users.dependencies import get_current_user, get_user_service
 from v1.users.schemas import UserSearchRequest, UserUpdateRequest
 from v1.users.service import UserService