Remove token revocation logic and unused dependencies

Eliminated the `RevokedToken` model and associated logic for managing token revocation. Removed unused files, related tests, and outdated dependencies in authentication modules. Simplified token decoding, user validation, and dependency injection by streamlining the flow and enhancing maintainability.

backend/tests/conftest.py

@@ -9,7 +9,7 @@ from app.models import Event, GiftItem, GiftStatus, GiftPriority, GiftCategory,
     EventTheme, Guest, GuestStatus, ActivityType, ActivityLog, EmailTemplate, TemplateType, NotificationLog, \
     NotificationType, NotificationStatus
 from app.models.user import User
-from app.utils.test_utils import setup_test_db, teardown_test_db
+from app.utils.test_utils import setup_test_db, teardown_test_db, setup_async_test_db, teardown_async_test_db
 
 
 @pytest.fixture(scope="function")
@@ -30,6 +30,15 @@ def db_session():
     teardown_test_db(test_engine)
 
 
+@pytest.fixture(scope="function")  # Define a fixture
+async def async_test_db():
+    """Fixture provides new testing engine and session for each test run to improve isolation."""
+
+    test_engine, AsyncTestingSessionLocal = await setup_async_test_db()
+    yield test_engine, AsyncTestingSessionLocal
+    await teardown_async_test_db(test_engine)
+
+
 @pytest.fixture
 def mock_user(db_session):
     """Fixture to create and return a mock User instance."""
@@ -72,7 +81,6 @@ def event_fixture(db_session, mock_user):
     return event
 
 
-
 @pytest.fixture
 def gift_item_fixture(db_session, mock_user):
     """