Fix admin route access and backend configuration

- Added /admin redirect to login page in nginx config
- Fixed backend server.js route ordering for proper admin handling
- Updated authentication middleware and routes
- Added user management routes
- Configured PostgreSQL integration
- Updated environment configuration

Data/ApplicationDbContext.cs

@@ -0,0 +1,12 @@
+using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore;
+
+namespace SkyArtShop.Data;
+
+public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
+{
+	public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
+		: base((DbContextOptions)options)
+	{
+	}
+}