refactor: 项目更名为 DiAL（统一拨测平台）

将 gateway-checker/Gateway Checker 统一替换为 dial-server/DiAL
- 包名、可执行文件名、API service 标识改为 dial-server
- UI 标题改为 DiAL，副标题改为统一拨测平台
- 同步更新测试断言、构建脚本、示例配置和文档

probes.example.yaml

@@ -99,13 +99,13 @@ targets:
     http:
       url: "https://httpbin.org/headers"
       headers:
-        X-Custom-Header: "gateway-checker"
+        X-Custom-Header: "dial-server"
     expect:
       status: [200]
       body:
         - json:
             path: "$.headers.X-Custom-Header"
-            equals: "gateway-checker"
+            equals: "dial-server"
 
   - name: "响应头自定义校验"
     type: http