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/api/admin/settings/paths/route.ts

@@ -14,7 +14,7 @@ export async function PUT(request: NextRequest) {
   return requireAuth(request, async (req: AuthenticatedRequest) => {
     return requireAdmin(req, async () => {
       try {
-        const { downloadDir, mediaDir, metadataTaggingEnabled, chapterMergingEnabled } = await request.json();
+        const { downloadDir, mediaDir, audiobookPathTemplate, metadataTaggingEnabled, chapterMergingEnabled } = await request.json();
 
         if (!downloadDir || !mediaDir) {
           return NextResponse.json(
@@ -44,6 +44,20 @@ export async function PUT(request: NextRequest) {
           create: { key: 'media_dir', value: mediaDir },
         });
 
+        // Update audiobook path template
+        if (audiobookPathTemplate !== undefined) {
+          await prisma.configuration.upsert({
+            where: { key: 'audiobook_path_template' },
+            update: { value: audiobookPathTemplate },
+            create: {
+              key: 'audiobook_path_template',
+              value: audiobookPathTemplate,
+              category: 'automation',
+              description: 'Template for organizing audiobook files in media directory',
+            },
+          });
+        }
+
         // Update metadata tagging setting
         await prisma.configuration.upsert({
           where: { key: 'metadata_tagging_enabled' },