Adapt + improve all public pages to the atom design system

Extended the same design-system treatment to the public site, faithful
to AtomCMS's "atom" theme. New src/components/public/ui.tsx provides the
signature atom building blocks + a scoped CSS layer:
- ContentCard: surface card with a primary-tinted header (icon circle +
  title + subtitle) and padded body — the atom content-card, used as
  every page's header and section wrapper.
- StatBlock / stat-grid, EmptyState, OnlineBadge (online/offline pill),
  RankBadge (medals for the top 3), and responsive .card-grid helpers.

Swept ~45 public pages (home/community/rankings hand-built as the
reference; the rest via parallel agents that read the schema and
preserved every query, server action, auth gate and field name):
heroes → ContentCard headers, lists → card-grids in ContentCards,
"no X" → EmptyState, status → OnlineBadge/RankBadge. The leaderboard
gained Credits/Diamonds/Duckets tabs (usersCurrency).

Behaviour unchanged. Verified on the prod server against amx_test: 15+
public pages render the content-cards/grids with real data, no errors;
computed styles confirm the tinted header, icon circle, medal + online
pills. Fixed an undefined --color-golden ref. tsc 0, vitest 49/49,
next build 0.

src/app/register/page.tsx

@@ -1,5 +1,6 @@
 import Link from "next/link";
 import { register } from "@/actions/register";
+import { ContentCard } from "@/components/public/ui";
 
 export default async function RegisterPage({
   searchParams,
@@ -9,13 +10,13 @@ export default async function RegisterPage({
   const { error } = await searchParams;
 
   return (
-    <main style={{ maxWidth: 400, margin: "2rem auto" }}>
-      <div className="card" style={{ padding: "1.75rem" }}>
-        <h1 style={{ marginTop: 0, textAlign: "center" }}>Create account</h1>
-        <p className="muted" style={{ textAlign: "center", marginTop: 0 }}>
-          Join the hotel — it only takes a moment.
-        </p>
-        <form action={register} style={{ display: "grid", gap: "0.7rem", marginTop: "1rem" }}>
+    <main style={{ maxWidth: 420, margin: "2rem auto" }}>
+      <ContentCard
+        icon="🎉"
+        title="Create account"
+        subtitle="Join the hotel — it only takes a moment."
+      >
+        <form action={register} style={{ display: "grid", gap: "0.7rem" }}>
           <input name="username" placeholder="Username" autoComplete="username" required />
           <input name="mail" type="email" placeholder="Email" autoComplete="email" required />
           <input
@@ -37,7 +38,7 @@ export default async function RegisterPage({
         <p className="muted" style={{ textAlign: "center", marginBottom: 0, marginTop: "1rem" }}>
           Already have an account? <Link href="/login">Sign in</Link>
         </p>
-      </div>
+      </ContentCard>
     </main>
   );
 }