fix: unhandled promise rejection in SearchableMultiSelect debounce

- Wrap onSearch call in .catch() to prevent Uncaught (in promise) errors
- Add console.warn to DashboardHubModel.loadDashboardSearchOptions catch
  for debugging visibility

frontend/src/lib/components/ui/SearchableMultiSelect.svelte

@@ -62,7 +62,10 @@
     searchQuery = e.target.value;
     if (debounceMs > 0 && onSearch) {
       clearTimeout(debounceTimer);
-      debounceTimer = setTimeout(() => onSearch(searchQuery), debounceMs);
+      debounceTimer = setTimeout(() => {
+        const result = onSearch(searchQuery);
+        if (result instanceof Promise) result.catch(() => {});
+      }, debounceMs);
     }
     if (!isOpen) isOpen = true;
   }

frontend/src/lib/models/DashboardHubModel.svelte.ts

@@ -391,7 +391,10 @@ export class DashboardHubModel {
         id: d.id, name: d.title, subtitle: d.slug || '',
         hint: d.last_modified ? formatDate(d.last_modified) : '',
       }));
-    } catch { this.searchableDashboardOptions = []; }
+    } catch {
+      this.searchableDashboardOptions = [];
+      console.warn('[DashboardHub] loadDashboardSearchOptions failed');
+    }
     finally { this.searchableDashboardLoading = false; }
   }