Add admin request deletion with soft delete and cleanup

Implements admin ability to delete requests with soft delete, media file cleanup, and seeding-aware torrent management. Adds new API endpoint, frontend confirmation dialog, and request actions dropdown. Updates database schema with deletedAt and deletedBy fields, and ensures all queries filter out deleted requests. Documentation added for feature and user flow.

src/lib/processors/retry-missing-torrents.processor.ts

@@ -21,10 +21,11 @@ export async function processRetryMissingTorrents(payload: RetryMissingTorrentsP
   await logger?.info('Starting retry job for requests awaiting search...');
 
   try {
-    // Find all requests in awaiting_search status
+    // Find all active requests in awaiting_search status
     const requests = await prisma.request.findMany({
       where: {
         status: 'awaiting_search',
+        deletedAt: null,
       },
       include: {
         audiobook: true,