i18n: Translate all Chinese to English across the codebase

Translate Chinese comments, log/error messages, validator labels and
Swagger annotations to English throughout the source code, generated
Swagger docs, config files and CI workflows.

Make the English README primary: README.md now holds the English docs
and README_EN.md holds the Chinese version, with cross-language links
updated accordingly.

Note: the generated docs/ swagger files were translated in place; run
`go generate ./...` (swag init) to regenerate them from the now-English
annotations when a Go toolchain is available.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

service/app_test.go

@@ -9,25 +9,25 @@ import (
 func TestGetAppVersion(t *testing.T) {
 	s := &AppService{}
 	v := s.GetAppVersion()
-	// 打印结果
+	// print result
 	t.Logf("App Version: %s", v)
 }
 
 func TestMultipleGetAppVersion(t *testing.T) {
 	s := &AppService{}
-	//并发测试
-	// 使用 WaitGroup 等待所有 goroutine 完成
+	//concurrency test
+	// use a WaitGroup to wait for all goroutines to finish
 	wg := sync.WaitGroup{}
-	wg.Add(10) // 启动 10 个 goroutine
-	// 启动 10 个 goroutine
+	wg.Add(10) // start 10   goroutine
+	// start 10   goroutine
 	for i := 0; i < 10; i++ {
 		go func() {
-			defer wg.Done() // 完成后减少计数
+			defer wg.Done() // decrement the count when done
 			v := s.GetAppVersion()
-			// 打印结果
+			// print result
 			t.Logf("App Version: %s", v)
 		}()
 	}
-	// 等待所有 goroutine 完成
+	// wait for all goroutine done
 	wg.Wait()
 }