- Migrated database sessions and operations to `AsyncSession` for full async support.
- Updated all service methods and dependencies (`get_db` to `get_async_db`) to support async logic.
- Refactored admin, user, organization, session-related CRUD methods, and routes with await syntax.
- Improved consistency and performance with async SQLAlchemy patterns.
- Enhanced logging and error handling for async context.
- Introduced `CRUDBaseAsync` for reusable async operations.
- Configured async database connection using SQLAlchemy 2.0 patterns with `asyncpg`.
- Added `deleted_at` column and soft delete functionality to the `User` model, including related Alembic migration.
- Optimized queries by adding composite indexes for common user filtering scenarios.
- Extended tests: added cases for token-based security utilities and user management endpoints.
