feat: add settings seed action and remove login credentials

SuperAdmins can seed once from Settings, and the login page no longer exposes default credentials.

src/api/seedApi.js

@@ -0,0 +1,7 @@
+// /src/api/seedApi.js
+import axiosInstance from './axiosInstance';
+
+export const seedApi = {
+  getStatus: () => axiosInstance.get('/seed/status'),
+  runSeed: () => axiosInstance.post('/seed', {}, { timeout: 60000 })
+};