Add in-memory report storage and async report handling

Introduced `InMemoryReportStorageWebExtension` to manage
reports in memory, enabling dynamic report storage and
retrieval. Updated `ReportViewer.razor` to conditionally
render the `DxReportViewer` component and initialize
reports asynchronously.

Configured dependency injection in `Program.cs` to register
`InMemoryReportStorageWebExtension` as a singleton and
integrated it with `CustomReportProvider`. Registered
`EnvelopeGenerator.ReceiverUI.PredefinedReports.Report` as
a trusted class for deserialization.

Enhanced `CustomReportProvider` to fetch reports from
memory or generate them dynamically using `ReportsFactory`.
Added necessary `using` directives and ensured proper
report lifecycle management.

EnvelopeGenerator.ReceiverUI/Services/InMemoryReportStorageWebExtension.cs

@@ -0,0 +1,83 @@
+using DevExpress.XtraReports.UI;
+using DevExpress.XtraReports.Web.Extensions;
+using EnvelopeGenerator.ReceiverUI.PredefinedReports;
+
+namespace EnvelopeGenerator.ReceiverUI.Services;
+
+public class InMemoryReportStorageWebExtension : ReportStorageWebExtension
+{
+    private const string DefaultReportName = "LargeDatasetReport";
+    private static readonly Dictionary<string, byte[]> Reports = new(StringComparer.OrdinalIgnoreCase);
+
+    public override bool CanSetData(string url) => IsValidUrl(url);
+
+    public override byte[] GetData(string url)
+    {
+        url = NormalizeUrl(url);
+
+        if (Reports.TryGetValue(url, out var reportLayout))
+            return reportLayout;
+
+        if (ReportsFactory.Reports.TryGetValue(url, out var reportFactory))
+            return SaveReport(reportFactory());
+
+        throw new DevExpress.XtraReports.Web.ClientControls.FaultException($"Report '{url}' was not found.");
+    }
+
+    public override Dictionary<string, string> GetUrls()
+    {
+        var urls = ReportsFactory.Reports.Keys
+            .Concat(Reports.Keys)
+            .Distinct(StringComparer.OrdinalIgnoreCase)
+            .ToDictionary(name => name, name => name, StringComparer.OrdinalIgnoreCase);
+
+        return urls;
+    }
+
+    public override bool IsValidUrl(string url)
+    {
+        return !string.IsNullOrWhiteSpace(url)
+            && url.IndexOfAny(Path.GetInvalidFileNameChars()) < 0;
+    }
+
+    public override void SetData(XtraReport report, string url)
+    {
+        url = NormalizeUrl(url);
+        Reports[url] = SaveReport(report);
+    }
+
+    public override string SetNewData(XtraReport report, string defaultUrl)
+    {
+        var url = NormalizeUrl(defaultUrl);
+        Reports[url] = SaveReport(report);
+        return url;
+    }
+
+    public bool TryGetReport(string url, out XtraReport report)
+    {
+        url = NormalizeUrl(url);
+
+        if (!Reports.ContainsKey(url))
+        {
+            report = null!;
+            return false;
+        }
+
+        using var stream = new MemoryStream(Reports[url]);
+        report = XtraReport.FromXmlStream(stream, true);
+        report.Name = url;
+        return true;
+    }
+
+    private static string NormalizeUrl(string url)
+    {
+        return string.IsNullOrWhiteSpace(url) ? DefaultReportName : url;
+    }
+
+    private static byte[] SaveReport(XtraReport report)
+    {
+        using var stream = new MemoryStream();
+        report.SaveLayoutToXml(stream);
+        return stream.ToArray();
+    }
+}