refactor: normalize date handling to Tehran timezone

- Updated date handling in BlogSeoFields and ScheduleSection to use Tehran timezone utilities for consistency.
- Introduced `toTehranClockTime`, `tehranWallClockToUnix`, and `todayIso` functions for accurate date representation.
- Modified various components to utilize these new utilities, ensuring that date strings are correctly formatted and timestamps are accurately converted.
- Enhanced API documentation to clarify the handling of date fields, emphasizing the importance of server-local midnight.
- Added tests to verify that date overrides and holidays maintain the correct day without shifting due to timezone discrepancies.

assets/admin/pages/PatientDetailPage.tsx

@@ -13,7 +13,7 @@ import { api } from '../lib/api';
 import type { ApiResponse } from '../lib/api';
 import type { PatientRecord } from '../types';
 import { useAuthStore } from '../stores/authStore';
-import { formatDate, formatDateTime, formatRial, formatTime, formatNumber } from '../lib/utils';
+import { formatDate, formatDateTime, formatRial, formatTime, formatNumber, unixToIso } from '../lib/utils';
 import DataTable, { type Column } from '../components/ui/DataTable';
 import type { WalletTxn } from '../hooks/usePatientWallet';
 import type { WalletModalSubmit } from '../components/WalletTransactionModal';
@@ -390,7 +390,7 @@ function MedicalRecordsTab({ uuid }: { uuid: string }) {
 
   const open = (m?: MedicalItem) => {
     setTitle(m?.title ?? ''); setBody(m?.body ?? '');
-    setDate(m?.recorded_at ? new Date(m.recorded_at * 1000).toISOString().slice(0, 10) : '');
+    setDate(unixToIso(m?.recorded_at));
     setModal(m ?? 'create');
   };