v0.3.5: restore full push notification system (14 channels)

Restored from v0.2.4:
- notifiers/: 14 push channels (bark/serverchan/telegram/lark/webhook/wechat/discord/smtp/...)
- push-user.service.ts: multi-user push config linked to cloud_configs.promotion_account
- notification.service.ts: full dispatcher with per-config + global fallback

New integrations:
- cloud.service.ts: notifyConfigEvent on save_success/cookie_expire/save_fail
- admin.routes.ts: 7 new API endpoints for push users, notify providers, channel test
- database.ts: migration for cloud_configs.notify_config column

How it works:
- Configure push channels in /admin/system-configs (global_notify_config JSON)
- Or per-cloud: link push_users.account = cloud_configs.promotion_account
- Notify events: save_success (green), cookie_expire (red), save_fail >=3 consecutive (yellow)

source_clean/src/database/database.ts

@@ -243,6 +243,13 @@ function migrateCloudConfigs(db: Database.Database): void {
   if (!hasPromotionAccount) {
     db.exec("ALTER TABLE cloud_configs ADD COLUMN promotion_account TEXT DEFAULT NULL");
     console.log('[DB] cloud_configs migration: promotion_account column added');
+
+  // v0.3.5: notify_config for per-cloud push notification settings
+  const hasNotifyConfig = db.prepare("SELECT sql FROM sqlite_master WHERE name='cloud_configs' AND sql LIKE '%notify_config%'").get();
+  if (!hasNotifyConfig) {
+    db.exec("ALTER TABLE cloud_configs ADD COLUMN notify_config TEXT DEFAULT NULL");
+    console.log('[DB] cloud_configs migration: notify_config column added');
+  }
   }
 }