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

Sky_Art_shop/Services/SlugService.cs

@@ -0,0 +1,33 @@
+using System.Text.RegularExpressions;
+
+namespace SkyArtShop.Services
+{
+    public class SlugService
+    {
+        public string GenerateSlug(string text)
+        {
+            if (string.IsNullOrWhiteSpace(text))
+                return string.Empty;
+
+            // Convert to lowercase
+            var slug = text.ToLowerInvariant();
+
+            // Replace spaces with hyphens
+            slug = slug.Replace(" ", "-");
+
+            // Replace & with "and"
+            slug = slug.Replace("&", "and");
+
+            // Remove invalid characters
+            slug = Regex.Replace(slug, @"[^a-z0-9\-]", "");
+
+            // Replace multiple hyphens with single hyphen
+            slug = Regex.Replace(slug, @"-+", "-");
+
+            // Trim hyphens from start and end
+            slug = slug.Trim('-');
+
+            return slug;
+        }
+    }
+}