feat(app): add prerender, self-hosted fonts and privacy page

Fonts come from npm, not Google, so no third-party font requests.
Pages are prerendered at build time; browser-only code is guarded.
nginx serves per-route HTML, a real 404 and gzip.

.gitea/workflows/build-Frontend-a.yml

@@ -66,6 +66,9 @@ jobs:
       - name: Build Production
         run: npx ng build --configuration production
 
+      - name: Prerender Check
+        run: npm run prerender:check
+
       # 5. Lighthouse Audit (Performance & SEO)
       - name: Lighthouse CI
         run: |