Convert admin pages to new Tailwind design pattern

- Replace 'card' class with 'admin-card' (gradient cards, dark mode support)
- Replace 'muted' class with consistent Tailwind muted states
- Standardize page headers with gradient backgrounds and Lucide icons
- Convert all inline styles to Tailwind classes
- Add admin-page CSS helpers (admin-card, admin-filter-bar, admin-section-title)
- Apply pattern to all 42 admin pages (was only 6 before)
- Zero TypeScript errors, production builds successfully

Co-authored-by: openhands <[email protected]>

src/app/admin/radio/history/page.tsx

@@ -1,6 +1,7 @@
 import Link from 'next/link';
 import { prisma } from '@/lib/prisma';
 import { StatusCard } from '@/components/admin/dashboard';
+import { Clock } from 'lucide-react';
 
 export const dynamic = 'force-dynamic';
 
@@ -74,7 +75,7 @@ export default async function AdminRadioHistoryPage() {
 
   return (
     <main>
-      <nav className="muted" style={{ marginBottom: '0.5rem' }}>
+      <nav className="text-xs text-gray-500 dark:text-gray-400 mb-2">
         <Link href="/admin/radio">Radio</Link> ·{' '}
         <Link href="/admin/radio/settings">Settings</Link> ·{' '}
         <Link href="/admin/radio/banners">Banners</Link> ·{' '}
@@ -82,15 +83,19 @@ export default async function AdminRadioHistoryPage() {
         <Link href="/admin/radio/history">History</Link>
       </nav>
 
-      <h1>Radio Play History</h1>
-      <p className="muted" style={{ marginTop: '-0.4rem' }}>
-        Past DJ shows and airtime (<code>radio_history</code>), most recent first.
-        Read-only log of who was on air, when, and how many listeners tuned in.
-      </p>
+      <div className="flex items-center gap-3 mb-6">
+        <div className="w-10 h-10 rounded-xl bg-gradient-to-br from-[var(--color-primary)]/20 to-[var(--color-primary)]/5 grid place-items-center">
+          <Clock size={20} className="text-[var(--color-primary)]" />
+        </div>
+        <div>
+          <h1 className="m-0 text-xl font-extrabold text-[var(--color-text)]">Radio Play History</h1>
+          <p className="m-0 text-xs text-[var(--color-text-muted)] mt-0.5">Past DJ shows and airtime (<code>radio_history</code>), most recent first. Read-only log of who was on air, when, and how many listeners tuned in.</p>
+        </div>
+      </div>
 
       {dbError ? (
-        <div className="card" style={{ marginBottom: '1.5rem' }}>
-          <p className="muted" style={{ margin: 0 }}>
+        <div className="admin-card mb-6">
+          <p className="text-xs text-gray-500 dark:text-gray-400 m-0">
             Could not load radio history (database unavailable).
           </p>
         </div>
@@ -109,12 +114,12 @@ export default async function AdminRadioHistoryPage() {
       )}
 
       {!dbError && history.length === 0 ? (
-        <p className="muted">No radio history recorded yet.</p>
+        <div className="admin-empty">No radio history recorded yet.</div>
       ) : null}
 
       {history.length > 0 ? (
         <section className="mt-6">
-          <h2>Show log ({history.length})</h2>
+          <h2 className="admin-section-title">Show log ({history.length})</h2>
           <table>
             <thead>
               <tr>
@@ -134,17 +139,17 @@ export default async function AdminRadioHistoryPage() {
                   <td>{String(h.id)}</td>
                   <td>{names.get(String(h.userId)) ?? `#${String(h.userId)}`}</td>
                   <td>{h.showName ?? '—'}</td>
-                  <td className="muted">{formatDate(h.startedAt)}</td>
+                  <td className="text-sm text-gray-500 dark:text-gray-400 whitespace-nowrap">{formatDate(h.startedAt)}</td>
                   <td>
                     {h.endedAt ? (
-                      <span className="muted">{formatDate(h.endedAt)}</span>
+                      <span className="text-sm text-gray-500 dark:text-gray-400">{formatDate(h.endedAt)}</span>
                     ) : (
                       <span className="inline-block text-[0.72rem] font-bold px-2 py-0.5 rounded-full bg-green-600/20 text-[var(--color-text)]">on air</span>
                     )}
                   </td>
-                  <td className="muted">{formatDuration(h.startedAt, h.endedAt)}</td>
+                  <td className="text-sm text-gray-500 dark:text-gray-400 whitespace-nowrap">{formatDuration(h.startedAt, h.endedAt)}</td>
                   <td>{h.listenersCount}</td>
-                  <td className="muted">{h.notes ?? '—'}</td>
+                  <td className="text-sm text-gray-500 dark:text-gray-400 whitespace-nowrap">{h.notes ?? '—'}</td>
                 </tr>
               ))}
             </tbody>