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).

.forgejo/workflows/docker-publish.yml

@@ -0,0 +1,28 @@
+name: Build and Publish Docker Image
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build-and-push:
+    runs-on: docker
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Log in to Codeberg Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: codeberg.org
+          username: ${{ github.repository_owner }}
+          # Requires a generated Application Token from your Codeberg settings saved as a repository secret
+          password: ${{ secrets.CODEBERG_TOKEN }}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: codeberg.org/${{ github.repository }}:latest