[PowerDisplay] Add custom vcp code name map and fix some bugs (#45355)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
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## Summary of the Pull Request
1. Fix quick access not working bug
2. Add custom value mapping
3. Fix some vcp slider visibility bug

demo for custom vcp value name mapping:
<img width="1399" height="744" alt="image"
src="https://github.com/user-attachments/assets/517e4dbb-409a-4e43-b15a-d0d31e59ce49"
/>
<img width="1379" height="337" alt="image"
src="https://github.com/user-attachments/assets/18f6f389-089c-4441-ad9f-5c45cac53814"
/>
<img width="521" height="1152" alt="image"
src="https://github.com/user-attachments/assets/27b5f796-66fa-4781-b16f-4770bebf3504"
/>
<img width="295" height="808" alt="image"
src="https://github.com/user-attachments/assets/54eaf5b9-5d54-4531-a40b-de3113122715"
/>


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and link it here: #xxx

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## Detailed Description of the Pull Request / Additional comments

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---------

Co-authored-by: Yu Leng <yuleng@microsoft.com>

src/settings-ui/Settings.UI/SettingsXAML/Views/PowerDisplayPage.xaml.cs

@@ -133,6 +133,65 @@ namespace Microsoft.PowerToys.Settings.UI.Views
             return ProfileHelper.GenerateUniqueProfileName(existingNames, baseName);
         }
 
+        // Custom VCP Mapping event handlers
+        private async void AddCustomMapping_Click(object sender, RoutedEventArgs e)
+        {
+            var dialog = new CustomVcpMappingEditorDialog(ViewModel.Monitors);
+            dialog.XamlRoot = this.XamlRoot;
+
+            var result = await dialog.ShowAsync();
+
+            if (result == ContentDialogResult.Primary && dialog.ResultMapping != null)
+            {
+                ViewModel.AddCustomVcpMapping(dialog.ResultMapping);
+            }
+        }
+
+        private async void EditCustomMapping_Click(object sender, RoutedEventArgs e)
+        {
+            if (sender is not Button button || button.Tag is not CustomVcpValueMapping mapping)
+            {
+                return;
+            }
+
+            var dialog = new CustomVcpMappingEditorDialog(ViewModel.Monitors);
+            dialog.XamlRoot = this.XamlRoot;
+            dialog.PreFillMapping(mapping);
+
+            var result = await dialog.ShowAsync();
+
+            if (result == ContentDialogResult.Primary && dialog.ResultMapping != null)
+            {
+                ViewModel.UpdateCustomVcpMapping(mapping, dialog.ResultMapping);
+            }
+        }
+
+        private async void DeleteCustomMapping_Click(object sender, RoutedEventArgs e)
+        {
+            if (sender is not Button button || button.Tag is not CustomVcpValueMapping mapping)
+            {
+                return;
+            }
+
+            var resourceLoader = ResourceLoaderInstance.ResourceLoader;
+            var dialog = new ContentDialog
+            {
+                XamlRoot = this.XamlRoot,
+                Title = resourceLoader.GetString("PowerDisplay_CustomMapping_Delete_Title"),
+                Content = resourceLoader.GetString("PowerDisplay_CustomMapping_Delete_Message"),
+                PrimaryButtonText = resourceLoader.GetString("Yes"),
+                CloseButtonText = resourceLoader.GetString("No"),
+                DefaultButton = ContentDialogButton.Close,
+            };
+
+            var result = await dialog.ShowAsync();
+
+            if (result == ContentDialogResult.Primary)
+            {
+                ViewModel.DeleteCustomVcpMapping(mapping);
+            }
+        }
+
         // Flag to prevent reentrant handling during programmatic checkbox changes
         private bool _isRestoringColorTempCheckbox;