feat: 品牌重命名 Sub2API -> TianShuAPI

- 前端: 所有界面显示、i18n 文本、组件中的品牌名称
- 后端: 服务层、设置默认值、邮件模板、安装向导
- 数据库: 迁移脚本注释
- 保持功能完全一致，仅更改品牌名称

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/internal/pkg/errors/http.go

@@ -1,21 +1,21 @@
-package errors
-
-import "net/http"
-
-// ToHTTP converts an error into an HTTP status code and a JSON-serializable body.
-//
-// The returned body matches the project's Status shape:
-// { code, reason, message, metadata }.
-func ToHTTP(err error) (statusCode int, body Status) {
-	if err == nil {
-		return http.StatusOK, Status{Code: int32(http.StatusOK)}
-	}
-
-	appErr := FromError(err)
-	if appErr == nil {
-		return http.StatusOK, Status{Code: int32(http.StatusOK)}
-	}
-
-	cloned := Clone(appErr)
-	return int(cloned.Code), cloned.Status
-}
+package errors
+
+import "net/http"
+
+// ToHTTP converts an error into an HTTP status code and a JSON-serializable body.
+//
+// The returned body matches the project's Status shape:
+// { code, reason, message, metadata }.
+func ToHTTP(err error) (statusCode int, body Status) {
+	if err == nil {
+		return http.StatusOK, Status{Code: int32(http.StatusOK)}
+	}
+
+	appErr := FromError(err)
+	if appErr == nil {
+		return http.StatusOK, Status{Code: int32(http.StatusOK)}
+	}
+
+	cloned := Clone(appErr)
+	return int(cloned.Code), cloned.Status
+}