feat(saas): Phase 3 桌面端 SaaS 集成 — 客户端、Store、UI、LLM 适配器

- saas-client.ts: SaaS HTTP 客户端 (登录/注册/Token/模型列表/Chat Relay/配置同步)
- saasStore.ts: Zustand 状态管理 (登录态、连接模式、可用模型、localStorage 持久化)
- connectionStore.ts: 集成 SaaS 模式分支 (connect() 优先检查 SaaS 连接模式)
- llm-service.ts: SaasLLMAdapter 实现 (通过 SaaS Relay 代理 LLM 调用)
- SaaSLogin.tsx: 登录/注册表单 (服务器地址、用户名、密码、邮箱)
- SaaSStatus.tsx: 连接状态展示 (账号信息、健康检查、可用模型列表)
- SaaSSettings.tsx: SaaS 设置页面入口 (登录态切换、功能列表)
- SettingsLayout.tsx: 添加 SaaS 平台菜单项
- store/index.ts: 导出 useSaaSStore

desktop/src/store/connectionStore.ts

@@ -213,6 +213,37 @@ export const useConnectionStore = create<ConnectionStore>((set, get) => {
       try {
         set({ error: null });
 
+        // === SaaS Relay Mode ===
+        // Check connection mode from localStorage (set by saasStore).
+        // This takes priority over Tauri/Gateway when the user has selected SaaS mode.
+        const savedMode = localStorage.getItem('zclaw-connection-mode');
+        if (savedMode === 'saas') {
+          const { loadSaaSSession, saasClient } = await import('../lib/saas-client');
+          const session = loadSaaSSession();
+
+          if (!session || !session.token || !session.saasUrl) {
+            throw new Error('SaaS 模式未登录，请先在设置中登录 SaaS 平台');
+          }
+
+          log.debug('Using SaaS relay mode:', session.saasUrl);
+
+          // Configure the singleton client
+          saasClient.setBaseUrl(session.saasUrl);
+          saasClient.setToken(session.token);
+
+          // Health check via GET /api/v1/relay/models
+          try {
+            await saasClient.listModels();
+          } catch (err) {
+            const errMsg = err instanceof Error ? err.message : String(err);
+            throw new Error(`SaaS 平台连接失败: ${errMsg}`);
+          }
+
+          set({ connectionState: 'connected', gatewayVersion: 'saas-relay' });
+          log.debug('Connected to SaaS relay');
+          return;
+        }
+
         // === Internal Kernel Mode (Tauri) ===
         // Check at RUNTIME, not at module load time, to ensure __TAURI_INTERNALS__ is available
         const useInternalKernel = isTauriRuntime();