feat: implement pngx-controller with Gitea CI/CD deployment

- Full FastAPI sync engine: master→replica document sync via paperless REST API
- Web UI: dashboard, replicas, logs, settings (Jinja2 + HTMX + Pico CSS)
- APScheduler background sync, SSE live log stream, Prometheus metrics
- Fernet encryption for API tokens at rest
- pngx.env credential file: written on save, pre-fills forms on load
- Dockerfile with layer-cached uv build, Python healthcheck
- docker-compose with host networking for Tailscale access
- Gitea Actions workflow: version bump, secret injection, docker compose deploy

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.dockerignore

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+.git
+.claude
+.env
+data/
+__pycache__
+*.pyc
+*.pyo
+.pytest_cache
+.mypy_cache
+*.egg-info
+dist/
+build/