feat(groups): improve rate multipliers modal UX

- Add user_name to GroupRateMultiplierEntry (backend + frontend)
- Compact row height with user ID, name, email display
- Add client-side pagination (15 per page)
- Add "Clear All" button with DELETE /admin/groups/:id/rate-multipliers
- Add i18n keys for new UI elements

backend/internal/handler/admin/admin_service_stub_test.go

@@ -179,6 +179,10 @@ func (s *stubAdminService) GetGroupRateMultipliers(_ context.Context, _ int64) (
 	return nil, nil
 }
 
+func (s *stubAdminService) ClearGroupRateMultipliers(_ context.Context, _ int64) error {
+	return nil
+}
+
 func (s *stubAdminService) ListAccounts(ctx context.Context, page, pageSize int, platform, accountType, status, search string, groupID int64) ([]service.Account, int64, error) {
 	return s.accounts, int64(len(s.accounts)), nil
 }

backend/internal/handler/admin/group_handler.go

@@ -360,6 +360,23 @@ func (h *GroupHandler) GetGroupRateMultipliers(c *gin.Context) {
 	response.Success(c, entries)
 }
 
+// ClearGroupRateMultipliers handles clearing all rate multipliers for a group
+// DELETE /api/v1/admin/groups/:id/rate-multipliers
+func (h *GroupHandler) ClearGroupRateMultipliers(c *gin.Context) {
+	groupID, err := strconv.ParseInt(c.Param("id"), 10, 64)
+	if err != nil {
+		response.BadRequest(c, "Invalid group ID")
+		return
+	}
+
+	if err := h.adminService.ClearGroupRateMultipliers(c.Request.Context(), groupID); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	response.Success(c, gin.H{"message": "Rate multipliers cleared successfully"})
+}
+
 // UpdateSortOrderRequest represents the request to update group sort orders
 type UpdateSortOrderRequest struct {
 	Updates []struct {

backend/internal/repository/user_group_rate_repo.go

@@ -98,7 +98,7 @@ func (r *userGroupRateRepository) GetByUserIDs(ctx context.Context, userIDs []in
 // GetByGroupID 获取指定分组下所有用户的专属倍率
 func (r *userGroupRateRepository) GetByGroupID(ctx context.Context, groupID int64) ([]service.UserGroupRateEntry, error) {
 	query := `
-		SELECT ugr.user_id, u.email, ugr.rate_multiplier
+		SELECT ugr.user_id, u.username, u.email, ugr.rate_multiplier
 		FROM user_group_rate_multipliers ugr
 		JOIN users u ON u.id = ugr.user_id
 		WHERE ugr.group_id = $1
@@ -113,7 +113,7 @@ func (r *userGroupRateRepository) GetByGroupID(ctx context.Context, groupID int6
 	var result []service.UserGroupRateEntry
 	for rows.Next() {
 		var entry service.UserGroupRateEntry
-		if err := rows.Scan(&entry.UserID, &entry.UserEmail, &entry.RateMultiplier); err != nil {
+		if err := rows.Scan(&entry.UserID, &entry.UserName, &entry.UserEmail, &entry.RateMultiplier); err != nil {
 			return nil, err
 		}
 		result = append(result, entry)

backend/internal/server/routes/admin.go

@@ -229,6 +229,7 @@ func registerGroupRoutes(admin *gin.RouterGroup, h *handler.Handlers) {
 		groups.DELETE("/:id", h.Admin.Group.Delete)
 		groups.GET("/:id/stats", h.Admin.Group.GetStats)
 		groups.GET("/:id/rate-multipliers", h.Admin.Group.GetGroupRateMultipliers)
+		groups.DELETE("/:id/rate-multipliers", h.Admin.Group.ClearGroupRateMultipliers)
 		groups.GET("/:id/api-keys", h.Admin.Group.GetGroupAPIKeys)
 	}
 }

backend/internal/service/admin_service.go

@@ -43,6 +43,7 @@ type AdminService interface {
 	DeleteGroup(ctx context.Context, id int64) error
 	GetGroupAPIKeys(ctx context.Context, groupID int64, page, pageSize int) ([]APIKey, int64, error)
 	GetGroupRateMultipliers(ctx context.Context, groupID int64) ([]UserGroupRateEntry, error)
+	ClearGroupRateMultipliers(ctx context.Context, groupID int64) error
 	UpdateGroupSortOrders(ctx context.Context, updates []GroupSortOrderUpdate) error
 
 	// API Key management (admin)
@@ -1271,6 +1272,13 @@ func (s *adminServiceImpl) GetGroupRateMultipliers(ctx context.Context, groupID
 	return s.userGroupRateRepo.GetByGroupID(ctx, groupID)
 }
 
+func (s *adminServiceImpl) ClearGroupRateMultipliers(ctx context.Context, groupID int64) error {
+	if s.userGroupRateRepo == nil {
+		return nil
+	}
+	return s.userGroupRateRepo.DeleteByGroupID(ctx, groupID)
+}
+
 func (s *adminServiceImpl) UpdateGroupSortOrders(ctx context.Context, updates []GroupSortOrderUpdate) error {
 	return s.groupRepo.UpdateSortOrders(ctx, updates)
 }

backend/internal/service/user_group_rate.go

@@ -5,6 +5,7 @@ import "context"
 // UserGroupRateEntry 分组下用户专属倍率条目
 type UserGroupRateEntry struct {
 	UserID         int64   `json:"user_id"`
+	UserName       string  `json:"user_name"`
 	UserEmail      string  `json:"user_email"`
 	RateMultiplier float64 `json:"rate_multiplier"`
 }