Add release blocklist feature

Introduce a per-request release blocklist to auto-block permanently failing releases and provide admin management. Changes include:

- Database: add BlockedRelease model (blocked_releases) to Prisma schema with unique (requestId, releaseKey) and indexes; documented in backend database docs.
- Service & utils: new blocklist.service, release-key and filter helpers for normalization and matching; processors updated to emit auto-blocks (monitor-download, organize-files, search processors, RSS).
- HTTP API: add admin endpoints GET/DELETE /api/admin/blocklist, DELETE /api/admin/blocklist/[id], and GET /api/admin/blocklist/by-request/[requestId].
- Admin UI: new /admin/blocklist page and numerous React components (toolbar, filters, table, rows, pagination, skeleton, chips, date picker) with URL-driven state hook and per-row unblock UX.
- Tests: add unit/integration tests for service, routes, utils, and updated processor tests.

The blocklist is idempotent (upsert), filters search results before ranking (interactive search shows badges only), and admin-only APIs require auth. This commit wires docs, API, DB, frontend and tests for the new feature.

src/app/admin/page.tsx

@@ -649,7 +649,7 @@ function AdminDashboardContent() {
             </div>
 
             {/* Quick Actions */}
-            <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-5 gap-4 mb-8">
+            <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4 mb-8">
               <Link
                 href="/admin/settings"
                 className="block p-6 bg-white dark:bg-gray-800 border border-gray-200 dark:border-gray-700 rounded-lg hover:shadow-md transition-all"
@@ -735,6 +735,30 @@ function AdminDashboardContent() {
                 </div>
               </Link>
 
+              <Link
+                href="/admin/blocklist"
+                className="block p-6 bg-white dark:bg-gray-800 border border-gray-200 dark:border-gray-700 rounded-lg hover:shadow-md transition-all"
+              >
+                <div className="flex items-center gap-3">
+                  <svg
+                    className="w-6 h-6 text-gray-600 dark:text-gray-400"
+                    fill="none"
+                    stroke="currentColor"
+                    viewBox="0 0 24 24"
+                  >
+                    <path
+                      strokeLinecap="round"
+                      strokeLinejoin="round"
+                      strokeWidth={2}
+                      d="M18.364 18.364A9 9 0 005.636 5.636m12.728 12.728A9 9 0 015.636 5.636m12.728 12.728L5.636 5.636"
+                    />
+                  </svg>
+                  <span className="font-medium text-gray-900 dark:text-gray-100">
+                    Blocklist
+                  </span>
+                </div>
+              </Link>
+
               <button
                 onClick={() => setIsBulkImportOpen(true)}
                 className="block p-6 bg-white dark:bg-gray-800 border border-gray-200 dark:border-gray-700 rounded-lg hover:shadow-md transition-all text-left"