ci: add GitHub Actions workflow to publish frontend to Pages

.github/workflows/deploy-frontend.yml

@@ -0,0 +1,45 @@
+name: Build & Publish Frontend to GitHub Pages
+
+on:
+  push:
+    branches: [ "main" ]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Use Node.js 18
+        uses: actions/setup-node@v4
+        with:
+          node-version: "18"
+
+      - name: Install & build frontend
+        working-directory: frontend
+        env:
+          VITE_API_BASE: ${{ secrets.FRONTEND_API_BASE }}
+          VITE_SOCKET_URL: ${{ secrets.FRONTEND_SOCKET_URL }}
+        run: |
+          npm ci
+          # ensure build-time env vars exist for Vite (safe defaults if secrets missing)
+          cat > .env.production <<EOV
+VITE_API_BASE=${{ secrets.FRONTEND_API_BASE }}
+VITE_SOCKET_URL=${{ secrets.FRONTEND_SOCKET_URL }}
+EOV
+          npm run build
+
+      - name: Upload build artifact for GitHub Pages
+        uses: actions/upload-pages-artifact@v1
+        with:
+          path: frontend/dist
+
+      - name: Deploy to GitHub Pages
+        uses: actions/deploy-pages@v1

.gitignore

@@ -0,0 +1,4 @@
+# local env and build artifacts
+.env.production
+frontend/dist/
+frontend/node_modules/