Introduce action

.gitea/workflows/workflow.yaml

@@ -0,0 +1,34 @@
+name: Build and deploy updated apps
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: https://github.com/actions/checkout@v4
+
+      - uses: https://github.com/actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - uses: https://github.com/pnpm/action-setup@v3
+        with: { version: 9, run_install: false }
+
+      - name: Install
+        run: pnpm install --frozen-lockfile
+
+      - name: Build only changed sites
+        env:
+          RANGE: ${{ github.event.pull_request.base.sha || github.event.before }}
+        run: |
+          echo "Building since $RANGE …"
+          pnpm turbo run build \
+            --filter "apps/*" \
+            --since "$RANGE" \
+            --concurrency 1