Fix hydra consent session parsing and audit detail tests

backend/internal/service/hydra_admin_service.go

@@ -240,14 +240,20 @@ func (s *HydraAdminService) ListConsentSessions(ctx context.Context, subject, cl
 	}
 	defer resp.Body.Close()
 
-	body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
+	if resp.StatusCode == http.StatusNoContent {
+		return []domain.HydraConsentSession{}, nil
+	}
+	body, _ := io.ReadAll(io.LimitReader(resp.Body, 1024*1024))
 	if resp.StatusCode >= 300 {
 		return nil, fmt.Errorf("hydra admin: list consent sessions failed status=%d body=%s", resp.StatusCode, string(body))
 	}
+	if len(body) == 0 {
+		return []domain.HydraConsentSession{}, nil
+	}
 
 	var sessions []domain.HydraConsentSession
 	if err := json.Unmarshal(body, &sessions); err != nil {
-		return nil, fmt.Errorf("hydra admin: decode consent sessions failed: %w", err)
+		return nil, fmt.Errorf("hydra admin: decode consent sessions failed: %w body=%s", err, string(body))
 	}
 	return sessions, nil
 }