refactor(sitecode): 统一各模块分销站点编码解析为公共包

- 新增 internal/sitecode 包：FromRequest 头优先解析、FromQueryThenHeader
  探测接口专用、ExtractHost/IsLocalHost 提取 Host 域名
- 替换 auth/order/listing/chat/notification/withdrawal/wallet/distribution
  八模块 17 处各自内联的解析逻辑，统一优先级与 TrimSpace 行为
- 修复 notification 漏 TrimSpace、探测接口会话头压过显式 query、
  GetPublicSiteInfo 把 localhost Host 当站点域名查库等不一致
- 顺手清理 auth 中无引用的 extractHost 死代码
- gofmt 修复 withdrawal/presenter、chat/file/payment 测试四个历史遗留格式问题

backend/internal/modules/withdrawal/handler.go

@@ -2,8 +2,8 @@ package withdrawal
 
 import (
 	"strconv"
-	"strings"
 
+	"hfb_sys/backend/internal/sitecode"
 	"hfb_sys/backend/pkg/response"
 
 	"github.com/gin-gonic/gin"
@@ -18,17 +18,7 @@ func NewHandler(service *Service) *Handler {
 }
 
 func parseSiteCode(c *gin.Context) string {
-	for _, val := range []string{
-		c.Query("distribution_site_code"),
-		c.Query("site_code"),
-		c.GetHeader("X-Distribution-Site-Code"),
-		c.GetHeader("X-Site-Code"),
-	} {
-		if trimmed := strings.TrimSpace(val); trimmed != "" {
-			return trimmed
-		}
-	}
-	return ""
+	return sitecode.FromRequest(c)
 }
 
 // ========== 用户端接口 ==========

backend/internal/modules/withdrawal/presenter.go

@@ -95,29 +95,29 @@ func (r *Repository) toDetailDTO(ctx context.Context, w model.WithdrawalRequest)
 		DistributionSiteName: siteName,
 		DistributionSiteCode: siteCode,
 		UserNickname:         user.Nickname,
-		UserPhone:          user.Phone,
-		AmountCent:         w.AmountCent,
-		FeeCent:            w.FeeCent,
-		ActualAmountCent:   w.ActualAmountCent,
-		PaymentAccountID:   w.PaymentAccountID,
-		AccountType:        w.AccountType,
-		AccountName:        w.AccountName,
-		AccountNo:          fullAccountNo,
-		BankName:           w.BankName,
-		BankBranch:         w.BankBranch,
-		CertificateURLs:    certificateURLs,
-		Status:             w.Status,
-		ReviewedBy:         w.ReviewedBy,
-		ReviewedByName:     reviewedByName,
-		ReviewedAt:         w.ReviewedAt,
-		ReviewRemark:       w.ReviewRemark,
-		PaidBy:             w.PaidBy,
-		PaidByName:         paidByName,
-		PaidAt:             w.PaidAt,
-		PaymentProofURL:    w.PaymentProofURL,
-		PaymentRemark:      w.PaymentRemark,
-		CreatedAt:          w.CreatedAt,
-		UpdatedAt:          w.UpdatedAt,
+		UserPhone:            user.Phone,
+		AmountCent:           w.AmountCent,
+		FeeCent:              w.FeeCent,
+		ActualAmountCent:     w.ActualAmountCent,
+		PaymentAccountID:     w.PaymentAccountID,
+		AccountType:          w.AccountType,
+		AccountName:          w.AccountName,
+		AccountNo:            fullAccountNo,
+		BankName:             w.BankName,
+		BankBranch:           w.BankBranch,
+		CertificateURLs:      certificateURLs,
+		Status:               w.Status,
+		ReviewedBy:           w.ReviewedBy,
+		ReviewedByName:       reviewedByName,
+		ReviewedAt:           w.ReviewedAt,
+		ReviewRemark:         w.ReviewRemark,
+		PaidBy:               w.PaidBy,
+		PaidByName:           paidByName,
+		PaidAt:               w.PaidAt,
+		PaymentProofURL:      w.PaymentProofURL,
+		PaymentRemark:        w.PaymentRemark,
+		CreatedAt:            w.CreatedAt,
+		UpdatedAt:            w.UpdatedAt,
 	}, nil
 }