Refactor authentication services to async password handling; optimize bulk operations and queries

- Updated `verify_password` and `get_password_hash` to their async counterparts to prevent event loop blocking.
- Replaced N+1 query patterns in `admin.py` and `session_async.py` with optimized bulk operations for improved performance.
- Enhanced `user_async.py` with bulk update and soft delete methods for efficient user management.
- Added eager loading support in CRUD operations to prevent N+1 query issues.
- Updated test cases with stronger password examples for better security representation.

backend/tests/crud/test_crud_error_paths.py

@@ -39,7 +39,7 @@ class TestCRUDErrorPaths:
         # Create first user
         user_data = UserCreate(
             email="unique@example.com",
-            password="Password123",
+            password="Password123!",
             first_name="First"
         )
         user_crud.create(db_session, obj_in=user_data)
@@ -52,7 +52,7 @@ class TestCRUDErrorPaths:
         """Test create handles other integrity errors."""
         user_data = UserCreate(
             email="integrityerror@example.com",
-            password="Password123",
+            password="Password123!",
             first_name="Integrity"
         )
 
@@ -71,7 +71,7 @@ class TestCRUDErrorPaths:
         """Test create handles unexpected errors."""
         user_data = UserCreate(
             email="unexpectederror@example.com",
-            password="Password123",
+            password="Password123!",
             first_name="Unexpected"
         )