fix(FN-3825): surface inline notification test feedback in settings

- Persist per-provider notification test results and render inline success/error feedback blocks
- Add ntfy "Test message notification" action wired to message-event test payload
- Keep toast notifications while also showing provider-specific status text with aria-live feedback
- Update SettingsModal tests to verify ntfy message-event call path and inline webhook/ntfy feedback rendering

Fusion-Task-Id: FN-3825

packages/dashboard/app/components/SettingsModal.css

@@ -1020,12 +1020,48 @@
 
 .notification-provider-actions {
   display: flex;
+  flex-wrap: wrap;
   gap: var(--space-sm);
   padding-top: var(--space-md);
   border-top: var(--btn-border-width) solid var(--border);
   margin-top: var(--space-md);
 }
 
+.notification-test-feedback {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-xs);
+  margin-top: var(--space-sm);
+}
+
+.notification-test-feedback-item {
+  border: var(--btn-border-width) solid var(--border);
+  border-radius: var(--radius-sm);
+  padding: var(--space-xs) var(--space-sm);
+}
+
+.notification-test-feedback-item--success {
+  border-color: color-mix(in srgb, var(--color-success) 45%, var(--border));
+  background: color-mix(in srgb, var(--color-success) 8%, transparent);
+  color: var(--color-success);
+}
+
+.notification-test-feedback-item--error {
+  border-color: color-mix(in srgb, var(--color-error) 45%, var(--border));
+  background: color-mix(in srgb, var(--color-error) 8%, transparent);
+  color: var(--color-error);
+}
+
+@media (max-width: 768px) {
+  .notification-provider-actions {
+    flex-direction: column;
+  }
+
+  .notification-provider-actions .btn {
+    width: 100%;
+  }
+}
+
 /* === Memory Settings === */
 .memory-status-message {
   display: flex;