feat(notifications): add Test button for ntfy and RSS with inline result

- POST /api/notifications/test/ntfy — sends a real push using current form
  values (not saved settings) so auth can be verified before saving; returns
  status + HTTP detail on success or error message on failure
- POST /api/notifications/test/rss — confirms the feed token exists and
  returns event count; no bill FK required
- NtfyTestRequest + NotificationTestResult schemas added
- Frontend: Test button next to Save on both ntfy and RSS sections; result
  shown inline as a green/red pill; uses current form state for ntfy so
  the user can test before committing

All future notification types should follow the same test-before-save pattern.

Authored-By: Jack Levy

frontend/lib/api.ts

@@ -165,6 +165,12 @@ export interface AnalysisStats {
   remaining: number;
 }
 
+export interface NotificationTestResult {
+  status: "ok" | "error";
+  detail: string;
+  event_count?: number;
+}
+
 // Notifications
 export const notificationsAPI = {
   getSettings: () =>
@@ -173,6 +179,16 @@ export const notificationsAPI = {
     apiClient.put<NotificationSettings>("/api/notifications/settings", data).then((r) => r.data),
   resetRssToken: () =>
     apiClient.post<NotificationSettings>("/api/notifications/settings/rss-reset").then((r) => r.data),
+  testNtfy: (data: {
+    ntfy_topic_url: string;
+    ntfy_auth_method: string;
+    ntfy_token: string;
+    ntfy_username: string;
+    ntfy_password: string;
+  }) =>
+    apiClient.post<NotificationTestResult>("/api/notifications/test/ntfy", data).then((r) => r.data),
+  testRss: () =>
+    apiClient.post<NotificationTestResult>("/api/notifications/test/rss").then((r) => r.data),
 };
 
 // Admin