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

CHANGELOG.md

@@ -0,0 +1,32 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Changed
+- **Python Version Baseline**: Updated minimum supported Python version from 3.8 to 3.11
+  - Root CLI package now requires Python >=3.11
+  - Added Python 3.12 support to CI and package classifiers
+  - Updated documentation to reflect 3.11+ minimum requirement
+  - Services and shared libraries already required Python 3.11+
+
+### CI/CD
+- Added Python 3.12 to CLI test matrix alongside 3.11
+- Updated CI workflows to test on newer Python versions
+
+### Documentation
+- Updated infrastructure documentation to consistently state Python 3.11+ minimum
+- Aligned all Python version references across docs
+
+## [0.1.0] - 2024-XX-XX
+
+Initial release with core AITBC functionality including:
+- CLI tools for blockchain operations
+- Coordinator API for job submission and management
+- Blockchain node implementation
+- GPU mining client support
+- SDK packages for integration