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>

lib/cache/simple_cache.go

@@ -6,7 +6,7 @@ import (
 	"sync"
 )
 
-// 此处实现了一个简单的缓存，用于测试
+// implements a simple cache used for testing
 // SimpleCache is a simple cache implementation
 type SimpleCache struct {
 	data      map[string]interface{}
@@ -19,21 +19,21 @@ func (s *SimpleCache) Get(key string, value interface{}) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	// 使用反射将存储的值设置到传入的指针变量中
+	// use reflection to set the stored value into the passed-in pointer variable
 	val := reflect.ValueOf(value)
 	if val.Kind() != reflect.Ptr {
 		return errors.New("value must be a pointer")
 	}
 	v, ok := s.data[key]
 	if !ok {
-		//设为空值
+		// set to zero value
 		val.Elem().Set(reflect.Zero(val.Elem().Type()))
 		return nil
 	}
 
 	vval := reflect.ValueOf(v)
 	if val.Elem().Type() != vval.Type() {
-		//设为空值
+		// set to zero value
 		val.Elem().Set(reflect.Zero(val.Elem().Type()))
 		return nil
 	}
@@ -45,7 +45,7 @@ func (s *SimpleCache) Get(key string, value interface{}) error {
 func (s *SimpleCache) Set(key string, value interface{}, exp int) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	// 检查传入的值是否是指针，如果是则取其值
+	// check whether the passed-in value is a pointer; if so, dereference it
 	val := reflect.ValueOf(value)
 	if val.Kind() == reflect.Ptr {
 		val = val.Elem()