feat(distribution): 分销站点消息中心与钱包提现多租户独立分支隔离

- 新增 000070 数据库迁移：支持 chat_conversations、wallet_accounts、wallet_ledger、withdrawal_requests 按 distribution_site_id 隔离
- 消息中心：会话列表、未读数统计、站点专属客服及订单群聊与主站实现双向完全隔离
- 资金账户与提现：独立按 (user_id, distribution_site_id) 建账，分销订单自动结算至对应分站钱包，提现与流水相互独立
- 前台界面：Axios 自动透传 X-Distribution-Site-Code，钱包、提现与消息页面呈现分站专属标牌与独立说明

backend/internal/modules/wallet/handler.go

@@ -3,6 +3,7 @@ package wallet
 import (
 	"errors"
 	"strconv"
+	"strings"
 
 	"hfb_sys/backend/internal/middleware"
 	"hfb_sys/backend/pkg/response"
@@ -18,13 +19,28 @@ func NewHandler(service *Service) *Handler {
 	return &Handler{service: service}
 }
 
+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 ""
+}
+
 func (h *Handler) Balance(c *gin.Context) {
 	userID, ok := currentUserID(c)
 	if !ok {
 		response.Unauthorized(c, "缺少用户上下文")
 		return
 	}
-	account, err := h.service.Account(c.Request.Context(), userID)
+	siteCode := parseSiteCode(c)
+	account, err := h.service.Account(c.Request.Context(), userID, siteCode)
 	if err != nil {
 		writeWalletError(c, err)
 		return
@@ -54,7 +70,8 @@ func (h *Handler) Ledger(c *gin.Context) {
 		return
 	}
 	page, pageSize := parsePagination(c)
-	result, err := h.service.Ledger(c.Request.Context(), userID, page, pageSize)
+	siteCode := parseSiteCode(c)
+	result, err := h.service.Ledger(c.Request.Context(), userID, page, pageSize, siteCode)
 	if err != nil {
 		writeWalletError(c, err)
 		return