bugfix: appointment hours now use the client timezone on UTC servers.

Logical API errors throw stable codes so users see translated messages instead of a generic bad request.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/ui/treatment/LabCasesDispatchPanel.tsx

@@ -20,6 +20,7 @@ import { prosthesisTypeColorFromCatalog } from '@/components/treatment/prosthesi
 import type { ProsthesisCatalogEntry, TreatmentCatalogEntry } from '@/types/treatment-catalog';
 import type { LabCaseDraft, LinkedOrganizationOption, TreatmentDetailDraft } from '@/types/treatment';
 import type { PatientLabCaseSummary } from '@/types/lab-case-activity';
+import { getUserFacingError } from '@/components/shared/formatApiError';
 import { groupsFromFlatTeeth } from '@/components/treatment/toothSelectionGroups';
 
 interface LabCasesDispatchPanelProps {
@@ -124,6 +125,7 @@ export function LabCasesDispatchPanel({
   onCommentError,
 }: LabCasesDispatchPanelProps) {
   const t = useTranslations('treatment');
+  const tErrors = useTranslations('errors');
   const [prosthesisOptions, setProsthesisOptions] = useState<ProsthesisCatalogEntry[]>([]);
   const [applyAllProsthesis, setApplyAllProsthesis] = useState('');
   const [pendingComment, setPendingComment] = useState('');
@@ -273,7 +275,7 @@ export function LabCasesDispatchPanel({
         taskProgress: response.data.taskProgress ?? activeLabCase.taskProgress,
       });
     } catch (error) {
-      onCommentError?.(error instanceof Error ? error.message : t('dueDateUpdateError'));
+      onCommentError?.(getUserFacingError(error, tErrors, t('dueDateUpdateError')));
     }
   }