feat: blocklist & search button for import-pending downloads with caution

- Poller now stores _instanceKey alongside _instanceUrl on Sonarr/Radarr queue records
- dashboard route threads arrQueueId/arrType/arrInstanceUrl/arrInstanceKey/arrContentId/arrContentType as admin-only fields on downloads with importIssues
- POST /api/dashboard/blocklist-search: admin-only, removes queue item with blocklist=true then triggers EpisodeSearch/MoviesSearch
- Button renders in download card header (admin + importIssues + arrQueueId only)
- Confirm dialog, loading/success/error states on the button
- Kicks a background poll on success so SSE reflects removed item promptly

public/style.css

@@ -1151,6 +1151,39 @@ body {
   pointer-events: none;
 }
 
+.blocklist-search-btn {
+  font-size: 0.68rem;
+  font-weight: 600;
+  padding: 2px 8px;
+  border-radius: 10px;
+  border: 1px solid var(--error, #e74c3c);
+  background: transparent;
+  color: var(--error, #e74c3c);
+  cursor: pointer;
+  white-space: nowrap;
+  transition: background 0.15s, color 0.15s;
+}
+
+.blocklist-search-btn:hover:not(:disabled) {
+  background: var(--error, #e74c3c);
+  color: #fff;
+}
+
+.blocklist-search-btn:disabled {
+  opacity: 0.6;
+  cursor: default;
+}
+
+.blocklist-search-btn.success {
+  border-color: var(--success, #27ae60);
+  color: var(--success, #27ae60);
+}
+
+.blocklist-search-btn.error {
+  background: var(--error, #e74c3c);
+  color: #fff;
+}
+
 .download-user-badge {
   padding: 2px 8px;
   border-radius: 10px;