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 Removed unused files, related tests, and outdated dependencies in authentication modules.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/app/utils/test_utils.py

@@ -1,5 +1,6 @@
 import logging
 from sqlalchemy import create_engine, event
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
 from sqlalchemy.orm import sessionmaker, clear_mappers
 from sqlalchemy.pool import StaticPool
 
@@ -42,4 +43,37 @@ def teardown_test_db(engine):
     Base.metadata.drop_all(engine)
 
     # Dispose of engine
-    engine.dispose()
+    engine.dispose()
+
+async def get_async_test_engine():
+    """Create an async SQLite in-memory engine specifically for testing"""
+    test_engine = create_async_engine(
+        "sqlite+aiosqlite:///:memory:",
+        connect_args={"check_same_thread": False},
+        poolclass=StaticPool,  # Use static pool for in-memory testing
+        echo=False
+    )
+    return test_engine
+
+
+async def setup_async_test_db():
+    """Create an async test database and session factory"""
+    test_engine = await get_async_test_engine()
+
+    async with test_engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+    AsyncTestingSessionLocal = sessionmaker(
+        autocommit=False,
+        autoflush=False,
+        bind=test_engine,
+        expire_on_commit=False,
+        class_=AsyncSession
+    )
+
+    return test_engine, AsyncTestingSessionLocal
+
+
+async def teardown_async_test_db(engine):
+    """Clean up after async tests"""
+    await engine.dispose()