Add Dockerfile, nginx config and publish CI

Add a multi-stage Dockerfile to build the React app (node:24-alpine, npm ci, npm run build) and serve the compiled /app/dist via nginx:alpine. Include nginx.conf that routes unknown paths to /index.html so React Router works in a SPA. Add a CI workflow (.forgejo/workflows/docker-publish.yml) to build and push the Docker image to Codeberg Container Registry on pushes to main (requires CODEBERG_TOKEN repository secret and tags the image as codeberg.org/${{ github.repository }}:latest).

Dockerfile

@@ -0,0 +1,14 @@
+# Compile the React application into static files
+FROM node:24-alpine AS builder
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci
+COPY . .
+RUN npm run build
+
+# Serve the static files using a lightweight web server
+FROM nginx:alpine
+COPY --from=builder /app/dist /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]