fix: keep birthdays and show Shamsi dates

Imported customers keep their birthday, and assistant text plus remaining calendars use the Jalali date.

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

apps/api/src/common/excel.ts

@@ -169,6 +169,28 @@ export function parseAmount(raw?: string): number | null {
   return Number.isFinite(n) ? n : null;
 }
 
+/** تاریخ تولد: سال زیر ۱۷۰۰ شمسی است، سال ۱۷۰۰ به بعد میلادی. ظهر UTC تا روز جابه‌جا نشود. */
+export function parseBirthDate(raw?: string | null): Date | null {
+  const text = toAsciiDigits(String(raw ?? '')).trim();
+  if (!text || text === '-' || text === '0' || text === '0000-00-00') return null;
+  const datePart = text.split(/[T\s]/)[0] ?? text;
+  const match = /^(\d{3,4})[\/\-.](\d{1,2})[\/\-.](\d{1,2})$/.exec(datePart);
+  if (!match) {
+    const fallback = new Date(text);
+    return Number.isNaN(fallback.getTime()) ? null : fallback;
+  }
+  const year = Number(match[1]);
+  const month = Number(match[2]);
+  const day = Number(match[3]);
+  if (month < 1 || month > 12 || day < 1 || day > 31) return null;
+  if (year >= 1700) {
+    return new Date(Date.UTC(year, month - 1, day, 12, 0, 0));
+  }
+  if (year < 1200) return null;
+  const { gy, gm, gd } = toGregorian(year, month, day);
+  return new Date(Date.UTC(gy, gm - 1, gd, 12, 0, 0));
+}
+
 export function parseJalaliDateTime(dateRaw?: string, timeRaw?: string): Date | null {
   const dateText = toAsciiDigits(dateRaw ?? '').trim();
   if (!dateText) return null;