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>

docker-compose.yml

@@ -0,0 +1,16 @@
+services:
+  pngx-controller:
+    build: .
+    restart: unless-stopped
+    network_mode: host          # required for Tailscale IP access (Linux only)
+    env_file: .env
+    environment:
+      DATABASE_URL: sqlite:////data/db.sqlite3
+    volumes:
+      - ./data:/data
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8000/healthz')"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 15s