RefGPT Agent Connector API

Version 0.1.26-PullRequest0018.21

Change log:
- Added WebSocket chat endpoint with streaming output
- Added API key authentication and organization-level key access
- Added Supabase integration for user, org, and book access control
- Added subscription-plan allowance checks and allowed-book resolution
- Added Qdrant source retrieval for citation-backed responses
- Added MCP lab page and agent MCP configuration support
- Added token usage tracking and structured NLog logging

Release version: True