chore: migrate to pnpm workspaces monorepo with Turborepo

- Restructure directories: apps/api, apps/admin, apps/website
- Add root pnpm-workspace.yaml, turbo.json, .prettierrc, .gitignore
- Rename packages to @inkreach/api, @inkreach/admin, @inkreach/website
- Add shared packages: packages/tsconfig, packages/shared-types
- Add pnpm.onlyBuiltDependencies for native builds
- Update docs: README.md, structs.md
- All three projects build successfully

apps/api/src/countries/dto/create-country.dto.ts

@@ -0,0 +1,14 @@
+import { ApiProperty } from '@nestjs/swagger';
+import { IsNotEmpty, IsOptional, IsString } from 'class-validator';
+
+export class CreateCountryDto {
+  @ApiProperty()
+  @IsString()
+  @IsNotEmpty()
+  countryName!: string;
+
+  @ApiProperty({ required: false, nullable: true })
+  @IsOptional()
+  @IsString()
+  countryIcon?: string;
+}