Fix mobile validation, cascade delete for businesses/categories, and DB error handling.

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

src/modules/auth/dto/request-otp.dto.ts

@@ -1,11 +1,10 @@
 import { ApiProperty } from '@nestjs/swagger';
-import { IsString, Matches } from 'class-validator';
+import { IsString } from 'class-validator';
+import { IsIranMobile } from '../../../common/decorators/is-iran-mobile.decorator';
 
 export class RequestOtpDto {
   @ApiProperty({ example: '09122222222' })
   @IsString()
-  @Matches(/^(\+?\d{10,15}|09\d{9})$/, {
-    message: 'mobile must be a valid mobile number',
-  })
+  @IsIranMobile()
   mobile!: string;
 }

src/modules/auth/dto/verify-otp.dto.ts

@@ -1,12 +1,11 @@
 import { ApiProperty } from '@nestjs/swagger';
 import { IsString, Matches } from 'class-validator';
+import { IsIranMobile } from '../../../common/decorators/is-iran-mobile.decorator';
 
 export class VerifyOtpDto {
   @ApiProperty({ example: '09122222222' })
   @IsString()
-  @Matches(/^(\+?\d{10,15}|09\d{9})$/, {
-    message: 'mobile must be a valid mobile number',
-  })
+  @IsIranMobile()
   mobile!: string;
 
   @ApiProperty({ example: '123456' })