fix: apply theme colors to all admin pages

AdminDashboard:
- Replace all gray colors with theme variables
- Indonesian text: 'Selamat datang', 'Kelola Plans', etc.
- Loading: 'Memuat...'

AdminPlans:
- bg-card, text-foreground, border-border
- text-muted-foreground for secondary text
- bg-muted for sections
- text-primary for links/icons
- text-destructive for delete
- Indonesian: 'Kelola Plans', 'Tambah Plan', 'Tidak ada plan'

AdminUsers:
- Same theme color replacements
- Indonesian: 'Kelola Users', 'Tidak ada user'
- bg-primary for avatars
- Consistent hover states

All pages now:
✅ Respect light/dark mode
✅ Use @theme colors from index.css
✅ Indonesian text (keeping English tech terms)
✅ Consistent with member layout styling

apps/web/src/components/admin/AdminBreadcrumb.tsx

@@ -0,0 +1,33 @@
+import { ChevronRight, Shield } from 'lucide-react'
+
+interface AdminBreadcrumbProps {
+  currentPage: string
+}
+
+const pageNames: Record<string, string> = {
+  '/admin': 'Dashboard',
+  '/admin/plans': 'Plans',
+  '/admin/payment-methods': 'Payment Methods',
+  '/admin/payments': 'Payments',
+  '/admin/users': 'Users',
+  '/admin/settings': 'Settings',
+}
+
+export function AdminBreadcrumb({ currentPage }: AdminBreadcrumbProps) {
+  const pageName = pageNames[currentPage] || 'Admin'
+
+  return (
+    <nav className="flex items-center space-x-1 text-sm text-muted-foreground">
+      <div className="flex items-center space-x-1">
+        <Shield className="h-4 w-4" />
+        <span>Admin</span>
+      </div>
+      {currentPage !== '/admin' && (
+        <>
+          <ChevronRight className="h-4 w-4" />
+          <span className="font-medium text-foreground">{pageName}</span>
+        </>
+      )}
+    </nav>
+  )
+}