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/components/requests/StatusBadge.tsx

@@ -64,6 +64,14 @@ export function StatusBadge({ status, progress, className }: StatusBadgeProps) {
       label: 'Cancelled',
       color: 'bg-gray-100 text-gray-800 dark:bg-gray-700 dark:text-gray-300',
     },
+    awaiting_approval: {
+      label: 'Pending Approval',
+      color: 'bg-yellow-100 text-yellow-800 dark:bg-yellow-900 dark:text-yellow-200',
+    },
+    denied: {
+      label: 'Request Denied',
+      color: 'bg-red-100 text-red-800 dark:bg-red-900 dark:text-red-200',
+    },
   };
 
   const config = statusConfig[status] || {