docs: Add release process and changelog

Add comprehensive release management documentation and changelog.

New files:
- .github/workflows/tag-release.md: Complete release process guide
  - Semantic versioning guidelines
  - 3 methods for creating releases (CLI, git, web UI)
  - Version bump guidelines (major/minor/patch)
  - Pre-release support (alpha/beta/rc)
  - Release checklist
  - Docker image tagging strategy
  - Example workflows

- CHANGELOG.md: Changelog following Keep a Changelog format
  - Unreleased section with all current features
  - Template for future releases
  - Adheres to Semantic Versioning

Release Process:
1. Create annotated git tag (e.g., v1.0.0)
2. Push tag to GitHub
3. GitHub Actions automatically:
   - Builds Docker image
   - Pushes with multiple tags (v1.0.0, 1.0, 1, latest)
   - Creates GitHub release with notes

Ready for v1.0.0 release!

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

CHANGELOG.md

@@ -0,0 +1,98 @@
+# 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]
+
+### Added
+- Initial project setup
+- Antigravity IDE (VSCode) with web-based VNC access
+- Happy Coder AI assistant integration
+- Automatic GitHub repository cloning on startup
+- Persistent home directory with ReadWriteMany PVC support
+- Secure non-root execution (claude user, UID 1000, GID 1000)
+- Support for private repositories via GitHub token
+- HTTPRoute (Gateway API) support
+- VNC password protection
+- Multi-platform Docker image builds
+- GitHub Actions CI/CD pipeline
+- Automated releases on version tags
+- Comprehensive deployment documentation (DEPLOYMENT.md)
+- Complete variables reference (VARIABLES.md)
+
+### Container Features
+- Base: jlesage/baseimage-gui:ubuntu-22.04-v4
+- Antigravity IDE (VSCode)
+- Happy Coder npm package
+- Chrome browser
+- Node.js (LTS)
+- Python 3
+- Git
+
+### Kubernetes Resources
+- StatefulSet with volumeClaimTemplates
+- ReadWriteMany PVC for /home directory
+- ConfigMap for configuration
+- Sealed Secrets support
+- HTTPRoute for external access
+- Service (headless)
+
+### Configuration Options
+- GitHub repository URL (required)
+- GitHub token (optional, for private repos)
+- VNC password (optional)
+- Happy Coder server URL (optional)
+- Happy Coder webapp URL (optional)
+- Display resolution (configurable)
+- Resource limits (configurable)
+- Storage size (configurable)
+
+### Documentation
+- README.md with quick start guide
+- DEPLOYMENT.md with step-by-step instructions
+- VARIABLES.md with complete variable reference
+- Release process documentation
+- Pull request template
+- Dependabot configuration
+
+## Version History
+
+No releases yet. See [Unreleased] section above for planned v1.0.0 features.
+
+---
+
+## Release Template
+
+Use this template for future releases:
+
+```markdown
+## [1.0.0] - YYYY-MM-DD
+
+### Added
+- New features
+- New configuration options
+
+### Changed
+- Changes to existing features
+- Updated dependencies
+
+### Deprecated
+- Features that will be removed in future versions
+
+### Removed
+- Removed features
+- Breaking changes
+
+### Fixed
+- Bug fixes
+- Security patches
+
+### Security
+- Security improvements
+- Vulnerability fixes
+```
+
+[Unreleased]: https://github.com/cpfarhood/devcontainer/compare/v1.0.0...HEAD