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/alerts/page.tsx

@@ -1,3 +1,4 @@
+import { Bell } from "lucide-react";
 import { sendHotelAlert } from "@/actions/admin-alerts";
 import { StatusCard } from "@/components/admin/dashboard";
 import { prisma } from "@/lib/prisma";
@@ -74,10 +75,15 @@ export default async function AdminAlerts() {
 
   return (
     <main>
-      <h1>Alerts</h1>
-      <p className="muted" style={{ marginTop: "-0.4rem" }}>
-        Read-only · 100 most recent alert_logs (newest first).
-      </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">
+          <Bell size={20} className="text-[var(--color-primary)]" />
+        </div>
+        <div>
+          <h1 className="m-0 text-xl font-extrabold text-[var(--color-text)]">Alerts</h1>
+          <p className="m-0 text-xs text-[var(--color-text-muted)] mt-0.5">Read-only · 100 most recent alert_logs (newest first).</p>
+        </div>
+      </div>
 
       <div className="grid grid-cols-[repeat(auto-fit,minmax(180px,1fr))] gap-3.5 mb-6">
         <StatusCard label="Alerts shown" value={alerts.length} icon="🔔" />
@@ -101,19 +107,19 @@ export default async function AdminAlerts() {
         />
       </div>
 
-      <form action={sendHotelAlert} className="card" style={{ marginBottom: "1.5rem" }}>
-        <h3 style={{ marginTop: 0 }}>Send hotel alert</h3>
-        <p className="muted" style={{ margin: "0 0 0.75rem" }}>
+      <form action={sendHotelAlert} className="admin-card mb-6">
+        <h3 className="mt-0">Send hotel alert</h3>
+        <p className="text-xs text-gray-500 dark:text-gray-400">
           Broadcasts a message to every online user via RCON (<code>hotelalert</code>).
         </p>
-        <div style={{ display: "flex", gap: "0.5rem", flexWrap: "wrap", alignItems: "flex-start" }}>
+        <div className="flex gap-2 flex-wrap items-start">
           <textarea
             name="message"
             required
             maxLength={1000}
             rows={2}
             placeholder="Message to broadcast to the hotel…"
-            style={{ flex: 1, minWidth: 240, resize: "vertical" }}
+            className="flex-1 min-w-[240px]"
           />
           <button type="submit" className="btn btn-primary">
             Send alert
@@ -121,12 +127,12 @@ export default async function AdminAlerts() {
         </div>
       </form>
 
-      <section className="card">
-        <h3 style={{ marginTop: 0 }}>Recent alerts ({alerts.length})</h3>
+      <section className="admin-card">
+        <h3 className="mt-0">Recent alerts ({alerts.length})</h3>
         {alerts.length === 0 ? (
-          <p className="muted">No alert logs.</p>
+          <div className="admin-empty">No alert logs.</div>
         ) : (
-          <div style={{ overflowX: "auto" }}>
+          <div className="overflow-x-auto">
             <table>
               <thead>
                 <tr>
@@ -139,7 +145,7 @@ export default async function AdminAlerts() {
               <tbody>
                 {alerts.map((a) => (
                   <tr key={String(a.id)}>
-                    <td className="muted" style={{ whiteSpace: "nowrap" }}>
+                    <td className="text-sm text-gray-500 dark:text-gray-400 whitespace-nowrap">
                       {fromDate(a.createdAt)}
                     </td>
                     <td>