Performance, SEO, a11y, and code quality improvements

1. Performance: 25 pages switched from force-dynamic to revalidate=300 (ISR);
   2 pages (community, developers) now fully static (SSG)
2. DB indexes: Added @@index on foreign keys for WebsiteArticles,
   WebsiteArticleReactions, WebsiteArticleComments, WebsiteHelpCenterTickets,
   WebsiteShopArticles, RadioSongRequests, StaffActivities
3. SEO: Added robots.ts, sitemap.ts, canonical URLs, Open Graph + Twitter
   Card metadata on root layout and news articles
4. A11Y: Replaced <details>/<summary> dropdowns with accessible button-based
   NavDropdown (aria-expanded, aria-haspopup, role=menu). MobileNav now
   uses translated aria-label, aria-expanded, aria-controls, role=menu
5. Code quality: Added try/catch to updateArticle/deleteArticle; deleteArticle
   now uses prisma. for atomicity
6. CI/CD: Added GitHub Actions workflow (typecheck + test)
7. i18n: Added openMenu/closeMenu keys to all 6 locales
8. Observability: Health endpoint now checks SMTP reachability when configured
9. Loading states: Added loading.tsx for root, admin, and news sections
10. Word filter cache: Added 60s TTL auto-refresh instead of manual cache bust

src/app/admin/loading.tsx

@@ -0,0 +1,7 @@
+export default function AdminLoading() {
+  return (
+    <div style={{ display: "flex", justifyContent: "center", padding: "4rem 0" }}>
+      <div className="animate-spin w-8 h-8 border-4 rounded-full" style={{ borderColor: "var(--color-primary)", borderTopColor: "transparent" }} />
+    </div>
+  );
+}