Refactor receiver suggestions filtering logic

Introduced `ReceiverSuggestionFilterHandler` to refine the
filtering of recent receiver suggestions based on name and
email. Added `SuggestionLimit` constant to replace hardcoded
limits and ensure consistency. Updated UI to use the new
`FilteredRecentSuggestions` property, which leverages the
`BuildFilteredRecentSuggestions` method for grouping,
ordering, and limiting suggestions. Adjusted
`OnDocumentSelectedAsync` to use the new constant. Added
necessary `@using` directive for the filter handler.

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Components/Sender/CreateEnvelopeWizardPopup.razor

@@ -2,6 +2,7 @@
 @using EnvelopeGenerator.Application.Common.Dto.Receiver
 @using EnvelopeGenerator.Application.Resources
 @using EnvelopeGenerator.Domain.Resources
+@using EnvelopeGenerator.Server.Client.Components.Sender.ReceiverSuggestionFilter
 @using EnvelopeGenerator.Server.Client.Services
 @using Microsoft.AspNetCore.Components.Forms
 @using Microsoft.Extensions.Localization
@@ -115,7 +116,7 @@
                     else if (_recentReceiverSuggestions.Count > 0)
                     {
                         <div class="sender-create-wizard__suggestion-list" role="listbox" aria-label="Recent receivers">
-                            @foreach (var suggestion in _recentReceiverSuggestions)
+                            @foreach (var suggestion in FilteredRecentSuggestions)
                             {
                                 <button type="button"
                                         class="sender-create-wizard__suggestion-item"
@@ -323,6 +324,8 @@
     private bool _isLoadingRecentSuggestions;
     private bool _recentSuggestionsLoaded;
 
+    private const int SuggestionLimit = 20;
+
     private byte[]? _documentBytes;
     private string? _documentFileName;
     private string _documentSizeText = string.Empty;
@@ -338,6 +341,9 @@
     private bool IsLastStep => _currentStep >= TotalSteps - 1;
     private bool CanSkipCurrentStep => _currentStep == 1;
 
+    private IReadOnlyList<RecentReceiverSuggestionDto> FilteredRecentSuggestions =>
+        BuildFilteredRecentSuggestions();
+
     private string CurrentStepTitle => _currentStep switch
     {
         0 => L("SenderWizard_Step_Basics", "Grunddaten"),
@@ -472,6 +478,23 @@
         return Task.CompletedTask;
     }
 
+    private IReadOnlyList<RecentReceiverSuggestionDto> BuildFilteredRecentSuggestions()
+    {
+        if (_recentReceiverSuggestions.Count == 0)
+            return [];
+
+        var handler = new ReceiverSuggestionFilterHandler(_recentReceiverSuggestions);
+        var filtered = handler.Filter(_receiverName, _receiverEmail);
+
+        return filtered
+            .GroupBy(x => x.EmailAddress, StringComparer.OrdinalIgnoreCase)
+            .Select(g => g.OrderByDescending(x => x.LastUsedAt).First())
+            .OrderByDescending(x => x.LastUsedAt)
+            .ThenBy(x => x.EmailAddress, StringComparer.OrdinalIgnoreCase)
+            .Take(SuggestionLimit)
+            .ToList();
+    }
+
     private async Task OnDocumentSelectedAsync(InputFileChangeEventArgs args)
     {
         if (IsActionLocked)
@@ -658,7 +681,7 @@
         _isLoadingRecentSuggestions = true;
         try
         {
-            var suggestions = await ReceiverService.GetRecentReceiverSuggestionsAsync(20);
+            var suggestions = await ReceiverService.GetRecentReceiverSuggestionsAsync(SuggestionLimit);
             _recentReceiverSuggestions.Clear();
             _recentReceiverSuggestions.AddRange(suggestions);
             _recentSuggestionsLoaded = true;
@@ -790,4 +813,5 @@
         var uiValue = UiLocalizer[key];
         return uiValue.ResourceNotFound ? fallback : uiValue.Value;
     }
+
 }