refactor(api): introduce UserContext schema for API dependency injection

Replace direct User database model imports in API endpoints with UserContext
schema, following the architecture principle that API routes should not import
database models directly.

Changes:
- Create UserContext schema in models/schema/auth.py with from_user() factory
- Update app/api/deps.py to return UserContext from all auth dependencies
- Add _get_user_model() helper for functions needing User model access
- Update 58 API endpoint files to use UserContext instead of User
- Add noqa comments for 4 legitimate edge cases (enums, internal helpers)

Architecture validation: 0 errors (down from 61), 11 warnings remain

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/api/v1/admin/admin_users.py

@@ -23,7 +23,8 @@ from app.api.deps import get_current_super_admin, get_current_super_admin_api
 from app.core.database import get_db
 from app.exceptions import ValidationException
 from app.services.admin_platform_service import admin_platform_service
-from models.database.user import User
+from models.database.user import User  # noqa: API-007 - Internal helper uses User model
+from models.schema.auth import UserContext
 
 router = APIRouter(prefix="/admin-users")
 logger = logging.getLogger(__name__)
@@ -142,7 +143,7 @@ def list_admin_users(
     limit: int = Query(100, ge=1, le=500),
     include_super_admins: bool = Query(True),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin),
+    current_admin: UserContext = Depends(get_current_super_admin),
 ):
     """
     List all admin users with their platform assignments.
@@ -165,7 +166,7 @@ def list_admin_users(
 def create_admin_user(
     request: CreateAdminUserRequest,
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin_api),
+    current_admin: UserContext = Depends(get_current_super_admin_api),
 ):
     """
     Create a new admin user (super admin or platform admin).
@@ -225,7 +226,7 @@ def create_admin_user(
 def get_admin_user(
     user_id: int = Path(...),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin),
+    current_admin: UserContext = Depends(get_current_super_admin),
 ):
     """
     Get admin user details with platform assignments.
@@ -241,7 +242,7 @@ def assign_admin_to_platform(
     user_id: int = Path(...),
     platform_id: int = Path(...),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin_api),
+    current_admin: UserContext = Depends(get_current_super_admin_api),
 ):
     """
     Assign an admin to a platform.
@@ -268,7 +269,7 @@ def remove_admin_from_platform(
     user_id: int = Path(...),
     platform_id: int = Path(...),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin_api),
+    current_admin: UserContext = Depends(get_current_super_admin_api),
 ):
     """
     Remove an admin's access to a platform.
@@ -295,7 +296,7 @@ def toggle_super_admin_status(
     user_id: int = Path(...),
     request: ToggleSuperAdminRequest = Body(...),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin_api),
+    current_admin: UserContext = Depends(get_current_super_admin_api),
 ):
     """
     Promote or demote an admin to/from super admin.
@@ -323,7 +324,7 @@ def toggle_super_admin_status(
 def get_admin_platforms(
     user_id: int = Path(...),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin),
+    current_admin: UserContext = Depends(get_current_super_admin),
 ):
     """
     Get all platforms assigned to an admin.
@@ -349,7 +350,7 @@ def get_admin_platforms(
 def toggle_admin_status(
     user_id: int = Path(...),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin_api),
+    current_admin: UserContext = Depends(get_current_super_admin_api),
 ):
     """
     Toggle admin user active status.
@@ -376,7 +377,7 @@ def toggle_admin_status(
 def delete_admin_user(
     user_id: int = Path(...),
     db: Session = Depends(get_db),
-    current_admin: User = Depends(get_current_super_admin_api),
+    current_admin: UserContext = Depends(get_current_super_admin_api),
 ):
     """
     Delete an admin user.