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

pytest.ini

@@ -20,16 +20,15 @@ addopts =
     --verbose
     --tb=short
 
-# Python path for imports (must match pyproject.toml)
+# Python path for imports
 pythonpath =
     .
-    packages/py/aitbc-core/src
     packages/py/aitbc-crypto/src
-    packages/py/aitbc-p2p/src
     packages/py/aitbc-sdk/src
     apps/coordinator-api/src
     apps/wallet-daemon/src
     apps/blockchain-node/src
+    apps/trade-exchange/src
 
 # Environment variables for tests
 env =