Add CI smoke screen check for frontend service

.github/workflows/frontend-docker-ci.yml

@@ -0,0 +1,49 @@
+name: Frontend Docker CI
+
+on:
+  push:
+    paths:
+      - "frontend/**"
+      - "docker/frontend.Dockerfile"
+      - ".github/workflows/frontend-docker-ci.yml"
+  pull_request:
+    paths:
+      - "frontend/**"
+      - "docker/frontend.Dockerfile"
+      - ".github/workflows/frontend-docker-ci.yml"
+
+jobs:
+  build-run-smoketest:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Build Docker image
+        run: docker build -f docker/frontend.Dockerfile -t listkeeper-frontend:ci .
+
+      - name: Run container
+        run: |
+          docker run -d --name frontend-ci -p 8080:80 listkeeper-frontend:ci
+          docker ps
+
+      - name: Smoke test homepage responds
+        run: |
+          # Try up to ~20 seconds for nginx to come up
+          for i in {1..20}; do
+            if curl -fsS http://localhost:8080 >/dev/null; then
+              echo "Frontend is serving ✅"
+              exit 0
+            fi
+            sleep 1
+          done
+
+          echo "Frontend did not become ready ❌"
+          echo "---- docker logs ----"
+          docker logs frontend-ci || true
+          exit 1
+
+      - name: Cleanup
+        if: always()
+        run: docker rm -f frontend-ci || true