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/fix-image-urls.js

@@ -0,0 +1,20 @@
+// Fix Product Image URLs - Replace absolute URLs with relative paths
+// Run this in browser console on admin page: http://skyarts.ddns.net/admin
+
+(async function () {
+  console.log("🔧 Fixing product image URLs...");
+
+  // This would need to be run server-side to fix MongoDB
+  // For now, manually edit the product with broken image through admin interface
+
+  console.log("⚠️ Manual fix required:");
+  console.log("1. Go to Admin → Products");
+  console.log(
+    '2. Find product with image: "http://localhost:5001/uploads/images/de3ee948-a476-40a6-b31b-d226549b762d.jpg"'
+  );
+  console.log("3. Edit the product");
+  console.log(
+    '4. In ImageUrl field, change to: "/uploads/images/de3ee948-a476-40a6-b31b-d226549b762d.jpg"'
+  );
+  console.log("5. Save");
+})();