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/analytics/presentation/dto/get-district-stats.dto.ts

@@ -1,9 +1,12 @@
 import { IsString } from 'class-validator';
+import { ApiProperty } from '@nestjs/swagger';
 
 export class GetDistrictStatsDto {
+  @ApiProperty({ description: 'City name' })
   @IsString()
   city!: string;
 
+  @ApiProperty({ description: 'Time period' })
   @IsString()
   period!: string;
 }