fix(intelligence): Heartbeat 统一健康系统 — 6处断链修复 + 健康面板 + SaaS自动恢复

Rust 后端 (heartbeat.rs):
- 告警实时推送: OnceLock<AppHandle> + Tauri emit heartbeat:alert
- 动态间隔: tokio::select! + Notify 替代不可变 interval
- Config 持久化: update_config 写入 VikingStorage
- heartbeat_init 从 VikingStorage 恢复 config
- 移除 dead code (subscribe, HeartbeatCheckFn)
- Memory stats fallback 分层处理

新增 health_snapshot.rs:
- HealthSnapshot Tauri 命令 — 按需查询引擎/记忆状态
- 注册到 lib.rs invoke_handler

前端修复:
- HeartbeatConfig handleSave 同步到 Rust 后端
- App.tsx 读 localStorage 持久化配置 + heartbeat:alert 监听 + toast
- saasStore 降级后指数退避探测恢复 + saas-recovered 事件
- 新增 HealthPanel.tsx 只读健康面板 (4卡片 + 告警列表)
- SettingsLayout 添加 health 导航入口

清理:
- 删除 intelligence-client/ 目录版 (9文件 -1640行, 单文件版是活跃代码)

desktop/src/components/HeartbeatConfig.tsx

@@ -31,6 +31,9 @@ import {
   type HeartbeatResult,
   type HeartbeatAlert,
 } from '../lib/intelligence-client';
+import { createLogger } from '../lib/logger';
+
+const log = createLogger('HeartbeatConfig');
 
 // === Default Config ===
 
@@ -312,9 +315,15 @@ export function HeartbeatConfig({ className = '', onConfigChange }: HeartbeatCon
     });
   }, []);
 
-  const handleSave = useCallback(() => {
+  const handleSave = useCallback(async () => {
     localStorage.setItem('zclaw-heartbeat-config', JSON.stringify(config));
     localStorage.setItem('zclaw-heartbeat-checks', JSON.stringify(checkItems));
+    // Sync to Rust backend (non-blocking — UI updates immediately)
+    try {
+      await intelligenceClient.heartbeat.updateConfig('zclaw-main', config);
+    } catch (err) {
+      log.warn('[HeartbeatConfig] Backend sync failed:', err);
+    }
     setHasChanges(false);
   }, [config, checkItems]);