Add atom-theme visual design (header/footer, theme system, restyled pages)

Faithful port of AtomCMS's "atom" theme look (light, Habbo-retro, golden
#eeb425 / amber #f59e0b accents, white cards, 12px radii, Nunito-first stack):
- globals.css: full token set + components (.site-header/.nav-item, .btn-*,
  .card, .hero, currency pills, article cards, inputs, tables, footer).
- SiteHeader (brand + nav + currency pills + auth box, staff-aware) + SiteFooter;
  layout wraps header/content/footer. Removed the bare SiteNav.
- Restyled home (hero + article cards), login (centered card).
- siteSettings now falls back to DEFAULTS on missing key OR DB error, so pages
  render without a DB; DATABASE_CONNECT_TIMEOUT_MS env + pool acquireTimeout make
  the no-DB fallback fast.

Verified in a real browser (computed styles): header white/sticky, golden logo
gradient, uppercase nav, amber primary button @12px radius, golden outline,
hero gradient — all correct. tsc exit 0, vitest 48/48, next build exit 0.

src/components/site-footer.tsx

@@ -0,0 +1,18 @@
+import { siteSettings } from "@/lib/services/site-settings";
+
+export async function SiteFooter() {
+  const hotelName = await siteSettings.get("hotel_name", "Atom");
+  const year = new Date().getFullYear();
+
+  return (
+    <footer className="site-footer">
+      <div className="inner">
+        <span>
+          © {year} {hotelName}
+        </span>
+        <span className="spacer" />
+        <span className="muted">AtomCMS → Next.js conversion</span>
+      </div>
+    </footer>
+  );
+}