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/cloud/notifiers/lark.notifier.ts

@@ -0,0 +1,39 @@
+import { Notifier, NotifyParams, NotifyResult, NotifierParam } from './notifier.types';
+
+const params: NotifierParam[] = [
+  { key: 'webhook_url', label: 'Webhook URL', type: 'url', required: true, placeholder: 'https://open.feishu.cn/open-apis/bot/v2/hook/xxx' },
+  { key: 'title', label: '\u6807\u9898', type: 'text', default: 'CloudSearch', required: false },
+  { key: 'content', label: '\u5185\u5bb9', type: 'text', required: true },
+  { key: 'level', label: '\u7ea7\u522b', type: 'text', default: 'info', required: false },
+];
+
+export const larkNotifier: Notifier = {
+  name: 'lark',
+  label: '\u98de\u4e66/Lark',
+  params,
+  async notify(p: NotifyParams): Promise<NotifyResult> {
+    try {
+      const level = p.level || 'info';
+      const template = level === 'error' ? 'red' : level === 'warn' ? 'orange' : 'blue';
+      const resp = await fetch(p.webhook_url, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({
+          msg_type: 'interactive',
+          card: {
+            header: { title: { tag: 'plain_text', content: p.title || 'CloudSearch' }, template },
+            elements: [
+              { tag: 'div', text: { tag: 'lark_md', content: p.content || '' } },
+              { tag: 'note', elements: [{ tag: 'plain_text', content: 'CloudSearch \u00b7 ' + new Date().toLocaleString('zh-CN', { timeZone: 'Asia/Shanghai' }) }] },
+            ],
+          },
+        }),
+      });
+      if (resp.ok) return { success: true, message: '\u98de\u4e66\u63a8\u9001\u6210\u529f' };
+      const text = await resp.text();
+      return { success: false, message: text.slice(0, 150) };
+    } catch (err: any) {
+      return { success: false, message: err.message };
+    }
+  },
+};