feat: code quality improvements and AI dev experience files

[Priyans-hu]

Summary

• Fixed auth routes to use Pydantic schemas for proper validation
• Removed debug print statement from pubsub.py
• Fixed bare except in websocket_manager.py to clean up dead connections
• Fixed current_user_controller response format (was using set notation)
• Added AI/dev experience files (CLAUDE.md, llms.txt, .cursorrules)

Changes

• app/routes/auth_routes.py - Use Pydantic schemas for request validation
• app/utils/pubsub.py - Remove debug print statement
• app/utils/websocket_manager.py - Handle dead websocket connections properly
• app/controllers/auth_controller.py - Fix response format

AI/Dev Files Added

• CLAUDE.md - Claude AI coding assistance guide
• llms.txt - AI crawler discoverability
• .cursorrules - Cursor IDE configuration

Test plan

• Verify auth endpoints work with proper validation
• Check websocket connections handled correctly
• Verify current user endpoint returns proper JSON