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

Dockerfile

@@ -0,0 +1,40 @@
+FROM golang:1.26-alpine AS builder
+
+WORKDIR /src/backend
+
+COPY backend/go.mod backend/go.sum ./
+RUN go mod download
+
+COPY backend/ ./
+
+ARG APP_VERSION=dev
+RUN CGO_ENABLED=0 GOOS=linux go build \
+  -trimpath \
+  -ldflags="-s -w -X main.version=${APP_VERSION}" \
+  -o /out/warpbox \
+  ./cmd/warpbox
+
+FROM alpine:3.22
+
+RUN apk add --no-cache ca-certificates ffmpeg wget
+
+ENV WARPBOX_ADDR=:8080 \
+    WARPBOX_DATA_DIR=/data \
+    WARPBOX_STATIC_DIR=/app/static \
+    WARPBOX_TEMPLATE_DIR=/app/templates
+
+WORKDIR /app
+
+COPY --from=builder /out/warpbox /usr/local/bin/warpbox
+COPY backend/static /app/static
+COPY backend/templates /app/templates
+
+RUN mkdir -p /data
+
+EXPOSE 8080
+VOLUME ["/data"]
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 \
+  CMD wget -qO- http://127.0.0.1:8080/health >/dev/null || exit 1
+
+ENTRYPOINT ["warpbox"]