Add SMS templates, prepaid IRT billing, and advertising shortcode 9000590009.

Charge ceil(len/64)*400 IRT per recipient across OTP, customer, and partner SMS; seed new businesses with 500k IRT; default partner sends to the advertising line.

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

src/auth/dto/send-otp.dto.ts

@@ -1,4 +1,4 @@
-import { IsOptional, IsString, Matches, MaxLength } from 'class-validator';
+import { IsString, Matches, MaxLength } from 'class-validator';
 
 export class SendOtpDto {
   @IsString()
@@ -7,9 +7,8 @@ export class SendOtpDto {
   })
   cellNumber!: string;
 
-  /** Tenant host/apex (e.g. sanihome.ir or business.sanihome.ir) — used to brand OTP SMS. */
-  @IsOptional()
+  /** Tenant host/apex — required so OTP SMS is billed to the business. */
   @IsString()
   @MaxLength(253)
-  domain?: string;
+  domain!: string;
 }