Update Python version requirements and fix compatibility issues

- Bump minimum Python version from 3.11 to 3.13 across all apps
- Add Python 3.11-3.13 test matrix to CLI workflow
- Document Python 3.11+ requirement in .env.example
- Fix Starlette Broadcast removal with in-process fallback implementation
- Add _InProcessBroadcast class for tests when Starlette Broadcast is unavailable
- Refactor API key validators to read live settings instead of cached values
- Update database models with explicit

apps/coordinator-api/src/app/config.py

@@ -118,7 +118,7 @@ class Settings(BaseSettings):
         if self.database.url:
             return self.database.url
         # Default SQLite path for backward compatibility
-        return f"sqlite:///./aitbc_coordinator.db"
+        return "sqlite:////home/oib/windsurf/aitbc/data/coordinator.db"
 
     @database_url.setter
     def database_url(self, value: str):