Add comments explaining why index.html dummy filename is needed for Scryber path resolution

Agent-Logs-Url: https://github.com/grandnode/grandnode2/sessions/5d2dbad8-02eb-4e9a-90c8-63cd785b237d

Co-authored-by: KrzysztofPajak <16772986+KrzysztofPajak@users.noreply.github.com>

Author: Copilot

src/Business/Grand.Business.Common/Services/Pdf/HtmlToPdfService.cs

@@ -44,6 +44,8 @@ public async Task PrintOrdersToPdf(Stream stream, IList<Order> orders, string la
         var html = await _viewRenderService.RenderToStringAsync(OrderTemplate,
             new ValueTuple<IList<Order>, string>(orders, vendorId));
         TextReader sr = new StringReader(html);
+        //Scryber uses Path.GetDirectoryName(LoadedSource) to resolve relative image paths,
+        //so we must pass a file path (not a directory) rooted in wwwroot.
         var basePath = Path.Combine(_webHostEnvironment.WebRootPath, "index.html");
         using var doc = Document.ParseDocument(sr, basePath, ParseSourceType.DynamicContent);
         doc.SaveAsPDF(stream);
@@ -80,6 +82,8 @@ public async Task PrintPackagingSlipsToPdf(Stream stream, IList<Shipment> shipme
 
         var html = await _viewRenderService.RenderToStringAsync(ShipmentsTemplate, shipments);
         TextReader sr = new StringReader(html);
+        //Scryber uses Path.GetDirectoryName(LoadedSource) to resolve relative image paths,
+        //so we must pass a file path (not a directory) rooted in wwwroot.
         var basePath = Path.Combine(_webHostEnvironment.WebRootPath, "index.html");
         using var doc = Document.ParseDocument(sr, basePath, ParseSourceType.DynamicContent);
         doc.SaveAsPDF(stream);