chore(lint): apply ruff --fix (4443 auto-fixes)

Auto-fixed categories:
- F401: unused imports removed
- I001: import blocks sorted
- W293: trailing whitespace stripped
- UP035: deprecated typing imports replaced
- SIM: simplify suggestions applied
- ARG: unused args prefixed with underscore
- T201: print statements removed
- F841: unused variables removed
- RUF059: unpacked variables prefixed

Remaining ~1500 unfixable errors (C901, B904, N806, E402) require manual work.

Backend smoke tests: 13/13 passed.

backend/src/api/auth.py

@@ -8,17 +8,19 @@
 # @RELATION DEPENDS_ON -> [is_adfs_configured]
 # @INVARIANT: All auth endpoints must return consistent error codes.
 
+import starlette.requests
 from fastapi import APIRouter, Depends, HTTPException, status
 from fastapi.security import OAuth2PasswordRequestForm
 from sqlalchemy.orm import Session
-from ..core.database import get_auth_db
-from ..services.auth_service import AuthService
-from ..schemas.auth import Token, User as UserSchema
-from ..dependencies import get_current_user
-from ..core.auth.oauth import oauth, is_adfs_configured
+
 from ..core.auth.logger import log_security_event
+from ..core.auth.oauth import is_adfs_configured, oauth
+from ..core.database import get_auth_db
 from ..core.logger import belief_scope
-import starlette.requests
+from ..dependencies import get_current_user
+from ..schemas.auth import Token
+from ..schemas.auth import User as UserSchema
+from ..services.auth_service import AuthService
 
 # #region router [C:1] [TYPE Variable]
 # @RELATION DEPENDS_ON -> [fastapi.APIRouter]