Refactor app architecture and clean local artifacts

Backend/Data/DesignTimeDbContextFactory.cs

@@ -1,5 +1,6 @@
 using Microsoft.EntityFrameworkCore;
 using Microsoft.EntityFrameworkCore.Design;
+using Microsoft.Extensions.Configuration;
 
 namespace Backend.Data;
 
@@ -7,9 +8,24 @@ public sealed class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<Awa
 {
     public AwardsDbContext CreateDbContext(string[] args)
     {
+        var environment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") ?? "Development";
+        var configuration = new ConfigurationBuilder()
+            .SetBasePath(Directory.GetCurrentDirectory())
+            .AddJsonFile("appsettings.json", optional: false)
+            .AddJsonFile($"appsettings.{environment}.json", optional: true)
+            .AddEnvironmentVariables()
+            .Build();
+
         var optionsBuilder = new DbContextOptionsBuilder<AwardsDbContext>();
-        var connectionString = Environment.GetEnvironmentVariable("VTSA_POSTGRES")
-            ?? "Host=localhost;Port=5432;Database=vtuber_star_awards;Username=postgres;Password=postgres";
+        var connectionString = configuration["VTSA_POSTGRES"]
+            ?? configuration.GetConnectionString("Postgres");
+
+        if (string.IsNullOrWhiteSpace(connectionString))
+        {
+            throw new InvalidOperationException(
+                "No PostgreSQL connection string configured for design-time EF operations. " +
+                "Set VTSA_POSTGRES or ConnectionStrings__Postgres before running dotnet ef.");
+        }
 
         optionsBuilder.UseNpgsql(connectionString);
         return new AwardsDbContext(optionsBuilder.Options);