Refactor import statements across multiple modules to use relative paths for better organization and maintainability.

Co-authored-by: Copilot <copilot@github.com>

backend/app/services/auth.py

@@ -6,7 +6,7 @@ from typing import Any
 from jose import JWTError, jwt
 from passlib.context import CryptContext
 
-from backend.app.db import get_conn, get_write_lock
+from ..db import get_conn, get_write_lock
 
 _pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")