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/bark.notifier.ts

@@ -0,0 +1,44 @@
+import { Notifier, NotifyParams, NotifyResult, NotifierParam } from './notifier.types';
+
+const params: NotifierParam[] = [
+{ key: 'key', label: 'Bark Key', type: 'text', required: true, placeholder: 'xxxxxxxxxxxxxxxxx' },
+    { key: 'server', label: '服务器', type: 'url', default: 'https://api.day.app', required: false, placeholder: 'https://api.day.app' },
+    { key: 'title', label: '标题', type: 'text', default: 'CloudSearch 通知', required: false },
+    { key: 'content', label: '内容', type: 'text', required: true },
+    { key: 'level', label: '级别', type: 'text', default: 'info', required: false },
+];
+
+export const barkNotifier: Notifier = {
+name: 'bark',
+    label: 'Bark',
+    params,
+    async notify(params) {
+        try {
+            const key = params.key;
+            const server = (params.server || 'https://api.day.app').replace(/\/+$/, '');
+            const title = params.title || 'CloudSearch';
+            const content = params.content || '';
+            const level = params.level || 'info';
+            const icon = level === 'error' ? '⚠️' : level === 'warn' ? '🔔' : 'ℹ️';
+            const resp = await fetch(`${server}/${key}`, {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({
+                    title: `${icon} ${title}`,
+                    body: content,
+                    group: 'CloudSearch',
+                    level: level === 'error' ? 'timeSensitive' : 'active',
+                    icon: '',
+                }),
+            });
+            if (!resp.ok) {
+                const text = await resp.text();
+                return { success: false, message: `HTTP ${resp.status}: ${text.slice(0, 100)}` };
+            }
+            return { success: true, message: 'Bark 推送成功' };
+        }
+        catch (err: any) {
+            return { success: false, message: err.message };
+        }
+    },
+};