refactor: split shared models and DTOs

src/ASTRAIN.Api/Program.cs

@@ -1,7 +1,10 @@
 using System.Text.RegularExpressions;
 using ASTRAIN.Api.Data;
 using ASTRAIN.Api.Services;
-using ASTRAIN.Shared;
+using ASTRAIN.Shared.Dtos;
+using ASTRAIN.Shared.Models;
+using ASTRAIN.Shared.Requests;
+using ASTRAIN.Shared.Responses;
 using Microsoft.EntityFrameworkCore;
 
 var builder = WebApplication.CreateBuilder(args);