feat: add hardened atomic staging deployment

.gitea/workflows/quality.yml

@@ -30,7 +30,9 @@ jobs:
       - name: Install browser
         run: npx playwright install --with-deps chromium
       - name: Unit and security tests
-        run: npm test
+        run: |
+          npm test
+          python3 tests/staging-deploy.test.py -v
       - name: Mobile browser acceptance
         run: |
           npm start > /tmp/timmy-server.log 2>&1 &
@@ -52,6 +54,8 @@ jobs:
       - name: Dependency audit
         run: npm audit --audit-level=high
       - name: Syntax checks
-        run: npm run check:syntax
+        run: |
+          npm run check:syntax
+          node --check tests/staging.acceptance.mjs
       - name: Diff hygiene
         run: npm run check:diff