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

packages/py/aitbc-crypto/pyproject.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 description = "AITBC cryptographic utilities for zero-knowledge proofs and digital signatures"
 readme = "README.md"
 license = {text = "MIT"}
-requires-python = ">=3.11"
+requires-python = ">=3.13"
 authors = [
     {name = "AITBC Team", email = "team@aitbc.dev"}
 ]
@@ -16,6 +16,7 @@ classifiers = [
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Topic :: Security :: Cryptography",
     "Topic :: Software Development :: Libraries :: Python Modules"
 ]