fix: restore ntfyDashboardHost setting and add schema protection for global settings

The ntfyDashboardHost field was incorrectly removed in 6346e22b as part of
an unrelated FN-672 commit. This restores the setting to GlobalSettings (moved
from ProjectSettings where it was misplaced), re-adds the UI field and deep
link handling, and adds schema protection so unknown keys in settings.json
survive code-level schema changes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/dashboard/app/App.tsx

@@ -190,6 +190,27 @@ function AppInner() {
       .catch(() => {/* keep empty array on failure */});
   }, []);
 
+  // Handle deep link to task on mount (from ntfy Click URLs)
+  useEffect(() => {
+    const params = new URLSearchParams(window.location.search);
+    const taskId = params.get("task");
+    if (!taskId) return;
+
+    // Clean URL immediately without reloading
+    const url = new URL(window.location.href);
+    url.searchParams.delete("task");
+    url.searchParams.delete("project");
+    window.history.replaceState({}, "", url.toString());
+
+    fetchTaskDetail(taskId)
+      .then((task) => {
+        handleDetailOpen(task);
+      })
+      .catch(() => {
+        addToast(`Task ${taskId} not found`, "error");
+      });
+  }, []); // eslint-disable-line react-hooks/exhaustive-deps
+
   // Favorite provider/model toggle handlers (shared by ListView bulk edit)
   const handleToggleFavorite = useCallback(async (provider: string) => {
     const currentFavorites = favoriteProviders;

packages/dashboard/app/components/SettingsModal.tsx

@@ -1584,6 +1584,28 @@ export function SettingsModal({
                   <small>When a task fails during execution (high priority)</small>
                 </div>
               </div>
+              <div className="form-group">
+                <label htmlFor="ntfyDashboardHost">Dashboard Hostname</label>
+                <input
+                  id="ntfyDashboardHost"
+                  type="text"
+                  placeholder="http://localhost:3000"
+                  value={form.ntfyDashboardHost || ""}
+                  onChange={(e) => {
+                    const val = e.target.value;
+                    setForm((f) => ({ ...f, ntfyDashboardHost: val || undefined }));
+                  }}
+                />
+                <small>
+                  Base URL for deep links in notifications. When set, clicking a notification
+                  opens the dashboard directly to the task.
+                </small>
+                {form.ntfyDashboardHost && !/^https?:\/\/.+/.test(form.ntfyDashboardHost) && (
+                  <small className="field-error">
+                    Must be a valid URL starting with http:// or https://
+                  </small>
+                )}
+              </div>
               </>
             )}
           </>