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

Models/AdminUser.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using MongoDB.Bson;
+using MongoDB.Bson.Serialization.Attributes;
+
+namespace SkyArtShop.Models;
+
+public class AdminUser
+{
+	[BsonId]
+	[BsonRepresentation(BsonType.ObjectId)]
+	public string? Id { get; set; }
+
+	[Required]
+	[EmailAddress]
+	public string Email { get; set; } = string.Empty;
+
+	[Required]
+	public string PasswordHash { get; set; } = string.Empty;
+
+	[Required]
+	public string Name { get; set; } = string.Empty;
+
+	[Required]
+	public string Role { get; set; } = "Admin";
+
+	public List<string> Permissions { get; set; } = new List<string>();
+
+	public bool IsActive { get; set; } = true;
+
+	public bool PasswordNeverExpires { get; set; } = true;
+
+	public DateTime? PasswordExpiresAt { get; set; }
+
+	public string CreatedBy { get; set; } = string.Empty;
+
+	public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+
+	public DateTime? LastLogin { get; set; }
+
+	public string Phone { get; set; } = string.Empty;
+
+	public string Notes { get; set; } = string.Empty;
+}