feat: add unified endpoint speed test for API providers

Add a comprehensive endpoint latency testing system that allows users to:
- Test multiple API endpoints concurrently
- Auto-select the fastest endpoint based on latency
- Add/remove custom endpoints dynamically
- View latency results with color-coded indicators

Backend (Rust):
- Implement parallel HTTP HEAD requests with configurable timeout
- Handle various error scenarios (timeout, connection failure, invalid URL)
- Return structured latency data with status codes

Frontend (React):
- Create interactive speed test UI component with auto-sort by latency
- Support endpoint management (add/remove custom endpoints)
- Extract and update Codex base_url from TOML configuration
- Integrate with provider presets for default endpoint candidates

This feature improves user experience when selecting optimal API endpoints,
especially useful for users with multiple provider options or proxy setups.

src/lib/tauri-api.ts

@@ -18,6 +18,13 @@ interface ImportResult {
   message?: string;
 }
 
+export interface EndpointLatencyResult {
+  url: string;
+  latency: number | null;
+  status?: number;
+  error?: string;
+}
+
 // Tauri API 封装，提供统一的全局 API 接口
 export const tauriAPI = {
   // 获取所有供应商
@@ -312,6 +319,22 @@ export const tauriAPI = {
       throw new Error(`检测 Claude 插件配置失败: ${String(error)}`);
     }
   },
+
+  // 第三方/自定义供应商：批量测试端点延迟
+  testApiEndpoints: async (
+    urls: string[],
+    options?: { timeoutSecs?: number },
+  ): Promise<EndpointLatencyResult[]> => {
+    try {
+      return await invoke<EndpointLatencyResult[]>("test_api_endpoints", {
+        urls,
+        timeout_secs: options?.timeoutSecs,
+      });
+    } catch (error) {
+      console.error("测速调用失败:", error);
+      throw error;
+    }
+  },
 };
 
 // 创建全局 API 对象，兼容现有代码