Refactor Gmail integration to use REST API with OAuth2

Implement data-source access control for SQL agent; add caching for user access profiles and enhance query processing with access validation

Implement admin user approval flow and enhance user status verification

Refactor token decoding logic to enhance support for asymmetric and symmetric JWTs

Enhance multi-agent pipeline with conversation memory and feedback logging

refactor: Simplify JWT verification by removing legacy HS256 support and unused functions

feat: Implement JWT token verification for secure API access