Restyle the admin panel to match AtomCMS's Filament housekeeping look

The admin pages used bare inline-styled tables on the default page
background. Rebuilt the admin shell + added a scoped .admin CSS layer so
the whole panel matches the original AtomCMS Filament look:
- Dark #2d2d44 sidebar (the AtomCMS admin navbar colour) with the nav
  grouped into Overview / Content / Users & access / Economy / Radio /
  System (mirrors the Filament resource groups), an avatar + rank badge
  header, and amber active-link highlighting via a client AdminNavLink
  (usePathname).
- A topbar ("Housekeeping" + signed-in user) over a light content area.
- Carded tables (surface bg, rounded, shadow, tinted header, row hover)
  and a page-title treatment, applied globally so every admin page is
  styled without per-page edits.

Verified in a real authenticated admin session (production server,
amx_test): sidebar renders #2d2d44 sticky, active link amber on dark
text, /admin/users table carded with 7 real rows; dev server serves the
admin rules after a cache refresh. tsc 0, vitest 49/49, next build 0.

src/app/admin/layout.tsx

@@ -1,12 +1,79 @@
-import Link from "next/link";
 import { redirect } from "next/navigation";
 import type { ReactNode } from "react";
+import { AdminNavLink } from "@/components/admin/admin-nav-link";
 import { requireStaff } from "@/lib/admin/guard";
 import { prisma } from "@/lib/prisma";
 import { siteSettings } from "@/lib/services/site-settings";
 
 export const dynamic = "force-dynamic";
 
+// Sidebar layout grouped like the original AtomCMS Filament panel (Content,
+// Users & access, Economy, Radio, System) instead of one flat list.
+const NAV_GROUPS: { label: string; items: { href: string; label: string }[] }[] = [
+  {
+    label: "Overview",
+    items: [{ href: "/admin", label: "Dashboard" }],
+  },
+  {
+    label: "Content",
+    items: [
+      { href: "/admin/articles", label: "Articles" },
+      { href: "/admin/tags", label: "Tags" },
+      { href: "/admin/navigation", label: "Navigator" },
+      { href: "/admin/help-questions", label: "Help center" },
+      { href: "/admin/ads", label: "Advertisements" },
+      { href: "/admin/photos", label: "Photos" },
+    ],
+  },
+  {
+    label: "Users & access",
+    items: [
+      { href: "/admin/users", label: "Users" },
+      { href: "/admin/bans", label: "Bans" },
+      { href: "/admin/ip", label: "IP management" },
+      { href: "/admin/applications", label: "Applications" },
+      { href: "/admin/teams", label: "Teams" },
+      { href: "/admin/permissions", label: "Permissions" },
+    ],
+  },
+  {
+    label: "Economy",
+    items: [
+      { href: "/admin/catalog", label: "Catalog" },
+      { href: "/admin/shop", label: "Shop" },
+      { href: "/admin/transactions", label: "Transactions" },
+      { href: "/admin/vouchers", label: "Vouchers" },
+      { href: "/admin/subscriptions", label: "Subscriptions" },
+      { href: "/admin/rare-values", label: "Rare values" },
+      { href: "/admin/badges", label: "Badges" },
+      { href: "/admin/achievements", label: "Achievements" },
+      { href: "/admin/calendar", label: "Calendar" },
+    ],
+  },
+  {
+    label: "Radio",
+    items: [
+      { href: "/admin/radio", label: "Radio" },
+      { href: "/admin/radio/history", label: "Radio history" },
+    ],
+  },
+  {
+    label: "System",
+    items: [
+      { href: "/admin/commandocentrum", label: "Commandocentrum" },
+      { href: "/admin/emulator", label: "Emulator" },
+      { href: "/admin/alerts", label: "Alerts" },
+      { href: "/admin/logs", label: "Logs" },
+      { href: "/admin/wordfilter", label: "Word filter" },
+      { href: "/admin/maintenance", label: "Maintenance" },
+      { href: "/admin/housekeeping", label: "Housekeeping" },
+      { href: "/admin/rooms", label: "Rooms" },
+      { href: "/admin/email-templates", label: "Email" },
+      { href: "/admin/settings", label: "Settings" },
+    ],
+  },
+];
+
 export default async function AdminLayout({ children }: { children: ReactNode }) {
   const staff = await requireStaff();
 
@@ -18,50 +85,42 @@ export default async function AdminLayout({ children }: { children: ReactNode })
     if (!u?.twoFactorConfirmedAt) redirect("/settings/2fa?error=staffrequired");
   }
 
+  const initial = staff.username.charAt(0).toUpperCase();
+
   return (
-    <div style={{ display: "grid", gridTemplateColumns: "190px 1fr", gap: "1.5rem" }}>
-      <aside className="card" style={{ height: "fit-content" }}>
-        <p className="muted" style={{ marginTop: 0 }}>
-          Staff · {staff.username} (rank {staff.rank})
-        </p>
-        <nav style={{ display: "grid", gap: "0.45rem" }}>
-          <Link href="/admin">Dashboard</Link>
-          <Link href="/admin/users">Users</Link>
-          <Link href="/admin/rooms">Rooms</Link>
-          <Link href="/admin/articles">Articles</Link>
-          <Link href="/admin/tags">Tags</Link>
-          <Link href="/admin/catalog">Catalog</Link>
-          <Link href="/admin/shop">Shop</Link>
-          <Link href="/admin/transactions">Transactions</Link>
-          <Link href="/admin/vouchers">Vouchers</Link>
-          <Link href="/admin/badges">Badges</Link>
-          <Link href="/admin/radio">Radio</Link>
-          <Link href="/admin/radio/history">Radio History</Link>
-          <Link href="/admin/achievements">Achievements</Link>
-          <Link href="/admin/subscriptions">Subscriptions</Link>
-          <Link href="/admin/calendar">Calendar</Link>
-          <Link href="/admin/rare-values">Rare Values</Link>
-          <Link href="/admin/photos">Photos</Link>
-          <Link href="/admin/bans">Bans</Link>
-          <Link href="/admin/applications">Applications</Link>
-          <Link href="/admin/help-questions">Help Center</Link>
-          <Link href="/admin/ads">Advertisements</Link>
-          <Link href="/admin/wordfilter">Word Filter</Link>
-          <Link href="/admin/ip">IP Management</Link>
-          <Link href="/admin/logs">Logs</Link>
-          <Link href="/admin/alerts">Alerts</Link>
-          <Link href="/admin/maintenance">Maintenance</Link>
-          <Link href="/admin/navigation">Navigator</Link>
-          <Link href="/admin/teams">Teams</Link>
-          <Link href="/admin/housekeeping">Housekeeping</Link>
-          <Link href="/admin/permissions">Permissions</Link>
-          <Link href="/admin/emulator">Emulator</Link>
-          <Link href="/admin/commandocentrum">Commandocentrum</Link>
-          <Link href="/admin/email-templates">Email</Link>
-          <Link href="/admin/settings">Settings</Link>
+    <div className="admin">
+      <aside className="admin-sidebar">
+        <div className="admin-sidebar-head">
+          <span className="admin-avatar" aria-hidden>
+            {initial}
+          </span>
+          <div style={{ minWidth: 0 }}>
+            <div className="admin-sidebar-name">{staff.username}</div>
+            <span className="admin-rank-badge">rank {staff.rank}</span>
+          </div>
+        </div>
+
+        <nav className="admin-nav">
+          {NAV_GROUPS.map((group) => (
+            <div key={group.label} className="admin-nav-group">
+              <span className="admin-nav-group-label">{group.label}</span>
+              {group.items.map((item) => (
+                <AdminNavLink key={item.href} href={item.href} label={item.label} />
+              ))}
+            </div>
+          ))}
         </nav>
       </aside>
-      <section>{children}</section>
+
+      <div className="admin-content">
+        <header className="admin-topbar">
+          <h2>Housekeeping</h2>
+          <span className="muted" style={{ fontSize: "0.8rem" }}>
+            Signed in as <strong>{staff.username}</strong>
+          </span>
+        </header>
+        <section className="admin-page">{children}</section>
+      </div>
     </div>
   );
 }