feat(api): add OpenAPI/Swagger documentation for all API endpoints

Install @nestjs/swagger, configure Swagger UI at /api/docs with JWT bearer
auth, and add ApiTags/ApiOperation/ApiResponse/ApiProperty decorators to
all 8 controllers (50+ endpoints) and 31 DTOs across auth, listings,
search, payments, subscriptions, admin, notifications, and analytics modules.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/modules/auth/presentation/dto/register.dto.ts

@@ -1,17 +1,22 @@
 import { IsString, IsOptional, IsEmail, MinLength } from 'class-validator';
+import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
 
 export class RegisterDto {
+  @ApiProperty({ example: '0901234567', description: 'Phone number' })
   @IsString()
   phone!: string;
 
+  @ApiProperty({ example: 'P@ssw0rd!', minLength: 8 })
   @IsString()
   @MinLength(8)
   password!: string;
 
+  @ApiProperty({ example: 'Nguyen Van A' })
   @IsString()
   @MinLength(1)
   fullName!: string;
 
+  @ApiPropertyOptional({ example: 'user@example.com' })
   @IsOptional()
   @IsEmail()
   email?: string;