fix(desktop): 替换 require() 为 ES import — 修复生产构建崩溃

- connectionStore: 2 处 require() → loadConversationStore() 异步预加载 + 闭包引用
- saasStore: 1 处 require() → await import()（logout 是 async）
- llm-service: 1 处 require() → 顶层 import（无循环依赖）
- streamStore: 移除重复动态导入，统一使用顶层 useConnectionStore
- tsc --noEmit 0 errors

desktop/src/lib/llm-service.ts

@@ -16,6 +16,7 @@
 
 import { DEFAULT_MODEL_ID, DEFAULT_OPENAI_BASE_URL } from '../constants/models';
 import { createLogger } from './logger';
+import { recordLLMUsage } from './telemetry-collector';
 
 const log = createLogger('LLMService');
 
@@ -819,7 +820,6 @@ function trackLLMCall(
   error?: unknown,
 ): void {
   try {
-    const { recordLLMUsage } = require('./telemetry-collector');
     recordLLMUsage(
       response.model || adapter.getProvider(),
       response.tokensUsed?.input ?? 0,
@@ -832,7 +832,7 @@ function trackLLMCall(
       },
     );
   } catch (e) {
-    log.debug('Telemetry recording failed (SSR or unavailable)', { error: e });
+    log.debug('Telemetry recording failed', { error: e });
   }
 }