Expose invoice locale on public payloads and accept English name fields on create customer.

Public invoices need branding defaultLocale for RTL viewers; customer create aligns with the business add-customer form.

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

src/customers/dto/create-customer.dto.ts

@@ -26,6 +26,16 @@ export class CreateCustomerDto {
   @MinLength(2)
   lastName!: string;
 
+  @IsOptional()
+  @IsString()
+  @MinLength(2)
+  firstNameEn?: string;
+
+  @IsOptional()
+  @IsString()
+  @MinLength(2)
+  lastNameEn?: string;
+
   @IsOptional()
   @IsEmail()
   email?: string;