Add request approval system and audiobook path template

Implements admin approval workflow for user requests with global and per-user auto-approve controls. Adds new request statuses ('awaiting_approval', 'denied'), related API endpoints, and UI for pending approvals. Introduces configurable audiobook organization path template with validation and preview in settings, updates database schema and migrations for new fields.

src/app/admin/logs/page.tsx

@@ -142,7 +142,7 @@ export default function AdminLogsPage() {
     <div className="min-h-screen bg-gray-50 dark:bg-gray-900">
       <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
         {/* Header */}
-        <div className="mb-8 flex items-center justify-between">
+        <div className="sticky top-0 z-10 mb-8 flex items-center justify-between bg-gray-50 dark:bg-gray-900 py-4 -mx-4 px-4 sm:-mx-6 sm:px-6 lg:-mx-8 lg:px-8 border-b border-gray-200 dark:border-gray-800">
           <div>
             <h1 className="text-3xl font-bold text-gray-900 dark:text-gray-100">
               System Logs