Initial commit of LittleShop project (excluding large archives)

- BTCPay Server integration
- TeleBot Telegram bot
- Review system
- Admin area
- Docker deployment configuration

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

LittleShop/Services/ProductService.cs

@@ -258,11 +258,11 @@ public class ProductService : IProductService
         var product = await _context.Products.FindAsync(photoDto.ProductId);
         if (product == null) return null;
 
-        var maxSortOrder = await _context.ProductPhotos
+        var existingPhotos = await _context.ProductPhotos
             .Where(pp => pp.ProductId == photoDto.ProductId)
-            .Select(pp => pp.SortOrder)
-            .DefaultIfEmpty(0)
-            .MaxAsync();
+            .ToListAsync();
+        
+        var maxSortOrder = existingPhotos.Any() ? existingPhotos.Max(pp => pp.SortOrder) : 0;
 
         var productPhoto = new ProductPhoto
         {