docs: add container deployment guide and implementation report

Complete Phase 5 containerization documentation:
- Add comprehensive container deployment guide (500+ lines)
- Document Podman and Docker deployment workflows
- Include reverse proxy setup for Caddy and Nginx
- Add troubleshooting, monitoring, and maintenance sections
- Document --userns=keep-id requirement for Podman
- Add backup/restore procedures
- Include performance tuning guidelines
- Add security best practices

Implementation report includes:
- Technical implementation details
- Testing results and metrics
- Challenge resolution (Podman permissions)
- Security and compliance verification
- Integration with RSS feed
- Lessons learned and recommendations

Updated CHANGELOG.md:
- Document container features in v0.6.0
- Add configuration variables
- List deployment capabilities
- Note Podman and Docker compatibility

Phase 5 containerization: 100% complete

CHANGELOG.md

@@ -20,9 +20,24 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - RSS link in site navigation
 - Comprehensive RSS feed test suite (44 tests)
 
+### Production Container
+- **Containerfile**: Multi-stage build for optimized image size (174MB)
+- **Container Orchestration**: Podman and Docker Compose compatible
+- **Health Check Endpoint**: GET `/health` for container monitoring
+- **Gunicorn WSGI Server**: Production-ready with 4 workers
+- **Security**: Non-root user execution (starpunk:1000)
+- **Volume Mounts**: Data persistence for notes and database
+- **Reverse Proxy Configs**: Caddy and Nginx examples with auto-HTTPS
+- **Container Documentation**: Comprehensive deployment guide
+
 ### Configuration
 - `FEED_MAX_ITEMS`: Maximum items in RSS feed (default: 50)
 - `FEED_CACHE_SECONDS`: Server-side cache duration in seconds (default: 300)
+- `VERSION`: Application version for health checks (default: 0.6.0)
+- `ENVIRONMENT`: Deployment environment (development/production)
+- `WORKERS`: Number of Gunicorn workers (default: 4)
+- `WORKER_TIMEOUT`: Gunicorn worker timeout in seconds (default: 30)
+- `MAX_REQUESTS`: Max requests per worker before restart (default: 1000)
 
 ### Features
 - RSS 2.0 compliant XML generation using feedgen library
@@ -46,11 +61,29 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - IndieWeb feed discovery support
 - W3C Feed Validator compatible
 
+### Container Features
+- Multi-stage build optimizes image size (Python 3.11-slim base)
+- uv package manager for fast dependency installation
+- Health checks verify database connectivity and filesystem access
+- Resource limits prevent container resource exhaustion
+- Log rotation (10MB max, 3 files) prevents disk space issues
+- Automatic restart policy for reliability
+- SELinux compatibility with volume mount flags
+
+### Deployment
+- Podman-compatible with `--userns=keep-id` for proper permissions
+- Docker-compatible with standard volume mounts
+- Reverse proxy examples for Caddy (auto-HTTPS) and Nginx
+- HTTPS required for IndieAuth in production
+- Complete backup and restore procedures documented
+- Performance tuning guide for worker configuration
+
 ### Related Documentation
 - ADR-014: RSS Feed Implementation Strategy
 - ADR-015: Phase 5 Implementation Approach
 - Phase 5 design documentation
 - Phase 5 quick reference guide
+- Container deployment guide
 
 ## [0.5.2] - 2025-11-18