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

docs/8_development/0_index.md

@@ -23,6 +23,8 @@ Build on the AITBC platform: APIs, SDKs, and contribution guides.
 | 15 | [15_ecosystem-initiatives.md](./15_ecosystem-initiatives.md) | Ecosystem roadmap |
 | 16 | [16_local-assets.md](./16_local-assets.md) | Local asset management |
 | 17 | [17_windsurf-testing.md](./17_windsurf-testing.md) | Testing with Windsurf |
+| 18 | [zk-circuits.md](./zk-circuits.md) | ZK proof circuits for ML |
+| 19 | [fhe-service.md](./fhe-service.md) | Fully homomorphic encryption |
 
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