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/app/layout.tsx

@@ -1,6 +1,7 @@
 import type { Metadata } from "next";
 import type { ReactNode } from "react";
-import { SiteNav } from "@/components/site-nav";
+import { SiteFooter } from "@/components/site-footer";
+import { SiteHeader } from "@/components/site-header";
 import "./globals.css";
 
 export const metadata: Metadata = {
@@ -12,8 +13,13 @@ export default function RootLayout({ children }: { children: ReactNode }) {
   return (
     <html lang="en">
       <body>
-        <SiteNav />
-        <div className="container">{children}</div>
+        <div style={{ display: "flex", flexDirection: "column", minHeight: "100vh" }}>
+          <SiteHeader />
+          <div className="container" style={{ flex: 1, width: "100%" }}>
+            {children}
+          </div>
+          <SiteFooter />
+        </div>
       </body>
     </html>
   );