feat(invitation): 支持分销站点自主配置返利比例与权限隔离

- 后端新增分站专属配置及审计接口（/api/distribution/invitation-config 等），基于分站管理员严格鉴权隔离
- 分销独立后台新增「邀请返利设置」页面（Invitations.tsx），支持分站管理员自主开启/调整返利比例并查看本站流水
- 主站后台邀请接口路径补齐 /admin 前缀，解决 404/401 鉴权作用域问题
- 验证方式：backend 单元测试全数通过，distribution-admin 类型与构建检查通过

backend/internal/modules/invitation/handler.go

@@ -1,6 +1,7 @@
 package invitation
 
 import (
+	"context"
 	"errors"
 	"net/http"
 	"strconv"
@@ -13,14 +14,23 @@ import (
 	"github.com/gin-gonic/gin"
 )
 
+type SiteScoper interface {
+	ScopeSiteID(ctx context.Context, adminID, requested uint64) (uint64, error)
+}
+
 type Handler struct {
-	service *Service
+	service    *Service
+	siteScoper SiteScoper
 }
 
 func NewHandler(service *Service) *Handler {
 	return &Handler{service: service}
 }
 
+func (h *Handler) SetSiteScoper(scoper SiteScoper) {
+	h.siteScoper = scoper
+}
+
 // GetInviteInfo 公开接口：根据邀请码查询邀请人简要信息（用于落地注册页）
 func (h *Handler) GetInviteInfo(c *gin.Context) {
 	code := strings.TrimSpace(c.Param("code"))
@@ -225,3 +235,131 @@ func writeInvitationError(c *gin.Context, err error) {
 		response.Error(c, http.StatusInternalServerError, "invitation_error", err.Error())
 	}
 }
+
+// DistributionGetConfig 分销端获取本站邀请返利比例配置
+func (h *Handler) DistributionGetConfig(c *gin.Context) {
+	siteID, err := h.resolveDistributionSiteID(c)
+	if err != nil {
+		response.Forbidden(c, "无权访问该分销站点")
+		return
+	}
+	cfg, err := h.service.GetRebateConfig(c.Request.Context(), siteID)
+	if err != nil {
+		writeInvitationError(c, err)
+		return
+	}
+	response.OK(c, cfg)
+}
+
+// DistributionUpdateConfig 分销端更新本站邀请返利比例配置
+func (h *Handler) DistributionUpdateConfig(c *gin.Context) {
+	siteID, err := h.resolveDistributionSiteID(c)
+	if err != nil {
+		response.Forbidden(c, "无权操作该分销站点")
+		return
+	}
+	if siteID == 0 {
+		response.BadRequest(c, "未指定有效分销站点")
+		return
+	}
+	var req UpdateConfigRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, "比例参数格式不正确，必须在0到1之间")
+		return
+	}
+	cfg, err := h.service.UpdateRebateConfig(c.Request.Context(), siteID, req)
+	if err != nil {
+		writeInvitationError(c, err)
+		return
+	}
+	response.OK(c, cfg)
+}
+
+// DistributionListInvitations 分销端查看本站邀请关系
+func (h *Handler) DistributionListInvitations(c *gin.Context) {
+	siteID, err := h.resolveDistributionSiteID(c)
+	if err != nil {
+		response.Forbidden(c, "无权访问该分销站点")
+		return
+	}
+	var query AdminInvitationQuery
+	if err := c.ShouldBindQuery(&query); err != nil {
+		response.BadRequest(c, "查询参数不正确")
+		return
+	}
+	query.DistributionSiteID = &siteID
+	items, total, err := h.service.ListAdminInvitations(c.Request.Context(), query)
+	if err != nil {
+		writeInvitationError(c, err)
+		return
+	}
+	response.OK(c, gin.H{
+		"items":     items,
+		"total":     total,
+		"page":      query.Page,
+		"page_size": query.PageSize,
+	})
+}
+
+// DistributionListRebates 分销端查看本站返利支出流水
+func (h *Handler) DistributionListRebates(c *gin.Context) {
+	siteID, err := h.resolveDistributionSiteID(c)
+	if err != nil {
+		response.Forbidden(c, "无权访问该分销站点")
+		return
+	}
+	var query AdminRebateLedgerQuery
+	if err := c.ShouldBindQuery(&query); err != nil {
+		response.BadRequest(c, "查询参数不正确")
+		return
+	}
+	query.DistributionSiteID = &siteID
+	items, total, err := h.service.ListAdminRebateLedgers(c.Request.Context(), query)
+	if err != nil {
+		writeInvitationError(c, err)
+		return
+	}
+	response.OK(c, gin.H{
+		"items":     items,
+		"total":     total,
+		"page":      query.Page,
+		"page_size": query.PageSize,
+	})
+}
+
+func (h *Handler) resolveDistributionSiteID(c *gin.Context) (uint64, error) {
+	adminID, _ := currentAdminID(c)
+	var requested uint64
+	if raw := c.Param("id"); raw != "" {
+		if id, err := strconv.ParseUint(raw, 10, 64); err == nil && id > 0 {
+			requested = id
+		}
+	}
+	if requested == 0 {
+		if raw := c.Query("site_id"); raw != "" {
+			if id, err := strconv.ParseUint(raw, 10, 64); err == nil && id > 0 {
+				requested = id
+			}
+		}
+	}
+	if requested == 0 {
+		if raw := c.Query("distribution_site_id"); raw != "" {
+			if id, err := strconv.ParseUint(raw, 10, 64); err == nil && id > 0 {
+				requested = id
+			}
+		}
+	}
+	if h.siteScoper != nil {
+		return h.siteScoper.ScopeSiteID(c.Request.Context(), adminID, requested)
+	}
+	return requested, nil
+}
+
+func currentAdminID(c *gin.Context) (uint64, bool) {
+	value, ok := c.Get(middleware.ContextAdminID)
+	if !ok {
+		return 0, false
+	}
+	adminID, ok := value.(uint64)
+	return adminID, ok
+}