feat: Enhance guest session pool management and concurrency handling

- Introduced new configuration constants for guest session management, including TTL and maintenance intervals.
- Refactored session creation and expiry logic to improve session lifecycle management.
- Implemented robust session validation and cleanup mechanisms to ensure efficient resource utilization.
- Added comprehensive tests for guest session pool concurrency and failure recovery scenarios.
- Updated logging to provide better insights into session pool operations and potential issues.
- Adjusted initialization logic to handle duplicate sessions gracefully and ensure unique user IDs in the pool.