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

Services/SlugService.cs

@@ -0,0 +1,20 @@
+using System.Text.RegularExpressions;
+
+namespace SkyArtShop.Services;
+
+public class SlugService
+{
+	public string GenerateSlug(string text)
+	{
+		if (string.IsNullOrWhiteSpace(text))
+		{
+			return string.Empty;
+		}
+		string text2 = text.ToLowerInvariant();
+		text2 = text2.Replace(" ", "-");
+		text2 = text2.Replace("&", "and");
+		text2 = Regex.Replace(text2, "[^a-z0-9\\-]", "");
+		text2 = Regex.Replace(text2, "-+", "-");
+		return text2.Trim('-');
+	}
+}