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/payments/presentation/dto/create-payment.dto.ts

@@ -6,29 +6,37 @@ import {
   MinLength,
 } from 'class-validator';
 import { Transform } from 'class-transformer';
+import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
 import { PaymentProvider, PaymentType } from '@prisma/client';
 
 export class CreatePaymentDto {
+  @ApiProperty({ enum: PaymentProvider, description: 'Payment provider' })
   @IsEnum(PaymentProvider)
   provider!: PaymentProvider;
 
+  @ApiProperty({ enum: PaymentType, description: 'Payment type' })
   @IsEnum(PaymentType)
   type!: PaymentType;
 
+  @ApiProperty({ type: Number, description: 'Amount in VND', example: 500000 })
   @Transform(({ value }) => BigInt(value))
   amountVND!: bigint;
 
+  @ApiProperty({ description: 'Payment description', example: 'Listing fee' })
   @IsString()
   @MinLength(1)
   description!: string;
 
+  @ApiProperty({ description: 'URL to redirect after payment', example: 'https://example.com/return' })
   @IsUrl()
   returnUrl!: string;
 
+  @ApiPropertyOptional({ description: 'External transaction ID' })
   @IsOptional()
   @IsString()
   transactionId?: string;
 
+  @ApiPropertyOptional({ description: 'Idempotency key to prevent duplicate payments' })
   @IsOptional()
   @IsString()
   idempotencyKey?: string;

apps/api/src/modules/payments/presentation/dto/list-transactions.dto.ts

@@ -1,17 +1,21 @@
 import { IsEnum, IsInt, IsOptional, Max, Min } from 'class-validator';
+import { ApiPropertyOptional } from '@nestjs/swagger';
 import { PaymentStatus } from '@prisma/client';
 
 export class ListTransactionsDto {
+  @ApiPropertyOptional({ enum: PaymentStatus, description: 'Filter by payment status' })
   @IsOptional()
   @IsEnum(PaymentStatus)
   status?: PaymentStatus;
 
+  @ApiPropertyOptional({ type: Number, description: 'Maximum number of results', minimum: 1, maximum: 100, default: 20 })
   @IsOptional()
   @IsInt()
   @Min(1)
   @Max(100)
   limit?: number;
 
+  @ApiPropertyOptional({ type: Number, description: 'Number of results to skip', minimum: 0, default: 0 })
   @IsOptional()
   @IsInt()
   @Min(0)

apps/api/src/modules/payments/presentation/dto/refund-payment.dto.ts

@@ -1,6 +1,8 @@
 import { IsString, MinLength } from 'class-validator';
+import { ApiProperty } from '@nestjs/swagger';
 
 export class RefundPaymentDto {
+  @ApiProperty({ description: 'Reason for the refund', example: 'Customer requested cancellation' })
   @IsString()
   @MinLength(1)
   reason!: string;