fix(test): add missing stub methods for RedeemCodeRepository and AdminService

Add ListByUserPaginated and SumPositiveBalanceByUser to redeemRepoStub
Add GetUserBalanceHistory to stubAdminService

Fixes CI test compilation errors

backend/internal/handler/admin/admin_service_stub_test.go

@@ -290,5 +290,9 @@ func (s *stubAdminService) ExpireRedeemCode(ctx context.Context, id int64) (*ser
 	return &code, nil
 }
 
+func (s *stubAdminService) GetUserBalanceHistory(ctx context.Context, userID int64, page, pageSize int, codeType string) ([]service.RedeemCode, int64, float64, error) {
+	return s.redeems, int64(len(s.redeems)), 100.0, nil
+}
+
 // Ensure stub implements interface.
 var _ service.AdminService = (*stubAdminService)(nil)

backend/internal/service/admin_service_delete_test.go

@@ -274,6 +274,14 @@ func (s *redeemRepoStub) ListByUser(ctx context.Context, userID int64, limit int
 	panic("unexpected ListByUser call")
 }
 
+func (s *redeemRepoStub) ListByUserPaginated(ctx context.Context, userID int64, params pagination.PaginationParams, codeType string) ([]RedeemCode, *pagination.PaginationResult, error) {
+	panic("unexpected ListByUserPaginated call")
+}
+
+func (s *redeemRepoStub) SumPositiveBalanceByUser(ctx context.Context, userID int64) (float64, error) {
+	panic("unexpected SumPositiveBalanceByUser call")
+}
+
 type subscriptionInvalidateCall struct {
 	userID  int64
 	groupID int64

backend/internal/service/admin_service_search_test.go

@@ -152,6 +152,14 @@ func (s *redeemRepoStubForAdminList) ListWithFilters(_ context.Context, params p
 	return s.listWithFiltersCodes, result, nil
 }
 
+func (s *redeemRepoStubForAdminList) ListByUserPaginated(_ context.Context, userID int64, params pagination.PaginationParams, codeType string) ([]RedeemCode, *pagination.PaginationResult, error) {
+	panic("unexpected ListByUserPaginated call")
+}
+
+func (s *redeemRepoStubForAdminList) SumPositiveBalanceByUser(_ context.Context, userID int64) (float64, error) {
+	panic("unexpected SumPositiveBalanceByUser call")
+}
+
 func TestAdminService_ListAccounts_WithSearch(t *testing.T) {
 	t.Run("search 参数正常传递到 repository 层", func(t *testing.T) {
 		repo := &accountRepoStubForAdminList{