- Add is_public column to bots table (migration 6.3.2-01)
- Add user_organizations to Diesel schema for org membership lookup
- Implement check_bot_access(): public bots allow all users, private bots
require user membership in the bot's organization via user_organizations
- Wire access check into websocket_handler before WS upgrade
- Read is_public from bots table instead of bot_configuration
- Add database_name field to Bot model
