Enhance grid filtering and sorting functionality

Updated `DxGrid` components for `_activeEnvelopes` and `_completedEnvelopes`:
- Disabled `ShowFilterRow` and added `FilterMenuButtonDisplayMode` to always display filter menu buttons.
- Enabled sorting for the `Id` column with descending order and added a display format.
- Added `EditSettings` to the `Status` column with a `DxComboBoxSettings` for filtering, using the new `GetStatusFilterItems` method.

Introduced `GetStatusFilterItems` to generate distinct status filter items and added a private `StatusFilterItem` record type for encapsulating status values and labels.

Made minor adjustments to grid layout auto-saving logic for consistency.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeSenderPage.razor

@@ -219,7 +219,8 @@
                         <DxGrid Data="@_activeEnvelopes"
                                 @ref="_gridActive"
                                 KeyFieldName="Id"
-                                ShowFilterRow="true"
+                                ShowFilterRow="false"
+                                FilterMenuButtonDisplayMode="GridFilterMenuButtonDisplayMode.Always"
                                 ShowSearchBox="true"
                                 AllowColumnReorder="true"
                                 AllowSort=true
@@ -237,6 +238,7 @@
                                 LayoutAutoSaving="OnActiveGridLayoutAutoSaving">
                             <Columns>
                                 <DxGridDataColumn FieldName="Id" Caption="ID"
+                                                  DisplayFormat="0"
                                                   SortIndex="0"
                                                   SortOrder="GridColumnSortOrder.Descending">
                                     <CellDisplayTemplate Context="cellContext">
@@ -249,6 +251,13 @@
                                     </CellDisplayTemplate>
                                 </DxGridDataColumn>
                                 <DxGridDataColumn FieldName="Status" Caption="@L("Status", "Status")" ExportEnabled="false">
+                                    <EditSettings>
+                                        <DxComboBoxSettings Data="@GetStatusFilterItems(_activeEnvelopes)"
+                                                            ValueFieldName="Value"
+                                                            TextFieldName="Text"
+                                                            SearchMode="ListSearchMode.AutoSearch"
+                                                            SearchFilterCondition="ListSearchFilterCondition.Contains" />
+                                    </EditSettings>
                                     <CellDisplayTemplate Context="cellContext">
                                         @{
                                             var envelope = cellContext.DataItem as EnvelopeDto;
@@ -376,7 +385,8 @@
                         <DxGrid Data="@_completedEnvelopes"
                                 @ref="_gridCompleted"
                                 KeyFieldName="Id"
-                                ShowFilterRow="true"
+                                ShowFilterRow="false"
+                                FilterMenuButtonDisplayMode="GridFilterMenuButtonDisplayMode.Always"
                                 ShowSearchBox="true"
                                 PageSize="20"
                                 PagerVisible="true"
@@ -391,6 +401,7 @@
                                 LayoutAutoSaving="OnCompletedGridLayoutAutoSaving">
                             <Columns>
                                 <DxGridDataColumn FieldName="Id" Caption="ID"
+                                                  DisplayFormat="0"
                                                   SortIndex="0"
                                                   SortOrder="GridColumnSortOrder.Descending">
                                     <CellDisplayTemplate Context="cellContext">
@@ -403,6 +414,13 @@
                                     </CellDisplayTemplate>
                                 </DxGridDataColumn>
                                 <DxGridDataColumn FieldName="Status" Caption="@L("Status", "Status")" ExportEnabled="false">
+                                    <EditSettings>
+                                        <DxComboBoxSettings Data="@GetStatusFilterItems(_completedEnvelopes)"
+                                                            ValueFieldName="Value"
+                                                            TextFieldName="Text"
+                                                            SearchMode="ListSearchMode.AutoSearch"
+                                                            SearchFilterCondition="ListSearchFilterCondition.Contains" />
+                                    </EditSettings>
                                     <CellDisplayTemplate Context="cellContext">
                                         @{
                                             var envelope = cellContext.DataItem as EnvelopeDto;
@@ -917,6 +935,16 @@
             .Take(20);
     }
 
+    IReadOnlyList<StatusFilterItem> GetStatusFilterItems(IEnumerable<EnvelopeDto>? source)
+    {
+        return (source ?? Enumerable.Empty<EnvelopeDto>())
+            .Select(x => x.Status)
+            .Distinct()
+            .OrderBy(x => x)
+            .Select(x => new StatusFilterItem(x, GetStatusLabel(x)))
+            .ToList();
+    }
+
     DateTime GetHistoryDate(HistoryDto history)
     {
         return history.ActionDate ?? history.AddedWhen;
@@ -1072,4 +1100,6 @@
         var json = JsonSerializer.Serialize(e.Layout);
         await UserPreferencesService.SaveGridLayoutAsync(GridKeyCompleted, json);
     }
+
+    private sealed record StatusFilterItem(EnvelopeStatus Value, string Text);
 }