feat: add Web UI for notification config (feishu + email)

- New config/notify_store.go: persistent notification config (notify.json)
- New API: GET/PUT /api/notify/config, POST /api/notify/test-feishu, POST /api/notify/test-email
- New Vue page: NotifyConfig.vue with feishu webhook and SMTP settings
- Updated cron/init to read from persistent store instead of env vars
- Password masked as ******** in API responses, preserved on updates

frontend/src/router/index.ts

@@ -2,6 +2,7 @@ import { createRouter, createWebHistory } from 'vue-router'
 import Dashboard from '../views/Dashboard.vue'
 import CertList from '../views/CertList.vue'
 import CertCreate from '../views/CertCreate.vue'
+import NotifyConfig from '../views/NotifyConfig.vue'
 import Login from '../views/Login.vue'
 import { isLoggedIn } from '../api'
 
@@ -32,6 +33,12 @@ const router = createRouter({
       component: CertCreate,
       meta: { requiresAuth: true },
     },
+    {
+      path: '/notify',
+      name: 'NotifyConfig',
+      component: NotifyConfig,
+      meta: { requiresAuth: true },
+    },
   ],
 })