feat: add Docker support and Gitea publish workflow

- Add a multi-stage Dockerfile for building and running the Go backend
- Add .dockerignore to optimize the Docker build context
- Create a Gitea Actions workflow to build and publish Docker images on tag push
- Register a new `/health` endpoint for container healthchecks
- Update README.md with Docker and Podman deployment instructions
- Ignore local `docker-compose.yml` in .gitignore

docker-compose.example.yml

@@ -0,0 +1,24 @@
+services:
+  warpbox-dev:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    image: warpbox-dev:local
+    env_file:
+      - .env
+    environment:
+      WARPBOX_ADDR: ":8080"
+      WARPBOX_DATA_DIR: /data
+      WARPBOX_STATIC_DIR: /app/static
+      WARPBOX_TEMPLATE_DIR: /app/templates
+    ports:
+      - "8080:8080"
+    volumes:
+      - ./data:/data:Z
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD-SHELL", "wget -qO- http://127.0.0.1:8080/health >/dev/null || exit 1"]
+      interval: 30s
+      timeout: 3s
+      start_period: 10s
+      retries: 3