fix export timezone and calendar month title

- Export now uses time.Now().In(loc) for year/month so users in
  positive UTC offsets get the correct month
- Export month title for Jalali/Hijri now correctly converts the
  first day of the Gregorian month to the target calendar instead
  of using the Gregorian month index to look up target month names

internal/bot/export.go

@@ -79,9 +79,11 @@ func GenerateMonthlyReport(store *db.Store, userID int64, timezone, accent, cale
 	var monthName string
 	switch calendar {
 	case "jalali":
-		monthName = fmt.Sprintf("%s %d", jalaliMonthNames[month-1], year)
+		jy, jm, _ := gregorianToJalali(year, int(month), 1)
+		monthName = fmt.Sprintf("%s %d", jalaliMonthNames[jm-1], jy)
 	case "hijri":
-		monthName = fmt.Sprintf("%s %d", hijriMonthNames[month-1], year)
+		hy, hm, _ := gregorianToHijri(year, int(month), 1)
+		monthName = fmt.Sprintf("%s %d", hijriMonthNames[hm-1], hy)
 	default:
 		monthName = time.Date(year, month, 1, 0, 0, 0, 0, time.UTC).Format("January 2006")
 	}