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>

http/controller/api/user.go

@@ -10,10 +10,10 @@ import (
 type User struct {
 }
 
-// currentUser 当前用户
-// @Tags 用户
-// @Summary 用户信息
-// @Description 用户信息
+// currentUser current user
+// @Tags user
+// @Summary user info
+// @Description user info
 // @Accept  json
 // @Produce  json
 // @Success 200 {object} apiResp.UserPayload
@@ -26,10 +26,10 @@ type User struct {
 //	c.JSON(http.StatusOK, up)
 //}
 
-// Info 用户信息
-// @Tags 用户
-// @Summary 用户信息
-// @Description 用户信息
+// Info user info
+// @Tags user
+// @Summary user info
+// @Description user info
 // @Accept  json
 // @Produce  json
 // @Success 200 {object} apiResp.UserPayload