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/contacts/dto.ts

@@ -293,6 +293,11 @@ export class CreatePersonDto {
   @MaxLength(200)
   instagram?: string;
 
+  @IsOptional()
+  @ValidateIf((_, v) => v !== '' && v != null)
+  @IsString()
+  birthDate?: string | null;
+
   @IsOptional()
   @IsString()
   @MaxLength(120)
@@ -401,6 +406,11 @@ export class UpdatePersonDto {
   @MaxLength(200)
   instagram?: string;
 
+  @IsOptional()
+  @ValidateIf((_, v) => v !== '' && v != null)
+  @IsString()
+  birthDate?: string | null;
+
   @IsOptional()
   @IsString()
   @MaxLength(120)