[Settings] Move title bar shutdown button to navigation view (#40714)

<!-- 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)?
-->
## Summary of the Pull Request

Based on
https://github.com/microsoft/PowerToys/pull/40260#issuecomment-3085099815
feedback, this PR remove the title bar shutdown button in favor of a
menu item in the navigation view footer.

- Menu item is visible only when tray icon is hidden
- A confirm dialog has been added

<img width="848" height="448" alt="image"
src="https://github.com/user-attachments/assets/529bcfa9-94ed-48b1-b2bb-ca6993d12e0f"
/>

<img width="848" height="448" alt="image"
src="https://github.com/user-attachments/assets/febafbb4-3a5b-4b04-8065-28f0d269ab6c"
/>

- Close is used in tray icon menu for closing app

<img alt="image"
src="https://github.com/user-attachments/assets/3ac79a8c-961f-4f95-8967-adef00aba77b"
/>

<img alt="image"
src="https://github.com/user-attachments/assets/c2800a77-c733-41a9-aa4f-fa4c2afd30a3"
/>

<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [x] **Closes:** #40346 #40577
- [x] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [x] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

- Open settings with tray icon visible: close menu is hidden
- Open settings with tray icon hidden: close menu is visible
- Tested close menu visibility change when tray icon option is changed
- Tested cancel button of close dialog
- Tested close button of dialog

---------

Co-authored-by: Niels Laute <niels.laute@live.nl>

src/settings-ui/Settings.UI/SettingsXAML/Views/ShellPage.xaml

@@ -1,4 +1,4 @@
-<UserControl
+<UserControl
     x:Class="Microsoft.PowerToys.Settings.UI.Views.ShellPage"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
@@ -39,17 +39,10 @@
             Margin="48,0,0,0"
             VerticalAlignment="Top"
             IsHitTestVisible="True">
-            <Grid.ColumnDefinitions>
-                <ColumnDefinition x:Name="LeftTitleBarColumn" Width="*" />
-                <ColumnDefinition x:Name="RightTitleBarColumn" Width="Auto" />
-            </Grid.ColumnDefinitions>
             <animations:Implicit.Animations>
                 <animations:OffsetAnimation Duration="0:0:0.3" />
             </animations:Implicit.Animations>
-            <StackPanel
-                Grid.Column="0"
-                HorizontalAlignment="Left"
-                Orientation="Horizontal">
+            <StackPanel Orientation="Horizontal">
                 <Image
                     Width="16"
                     Height="16"
@@ -71,24 +64,6 @@
                     TextWrapping="NoWrap"
                     Visibility="Collapsed" />
             </StackPanel>
-            <StackPanel
-                Grid.Column="1"
-                Margin="0,0,148,0"
-                HorizontalAlignment="Right"
-                Orientation="Horizontal">
-                <Button
-                    x:Name="ShutDownBtn"
-                    Height="48"
-                    Click="ExitPTItem_Tapped"
-                    Style="{StaticResource SubtleButtonStyle}">
-                    <FontIcon FontSize="16" Glyph="&#xE7E8;" />
-                    <ToolTipService.ToolTip>
-                        <ToolTip>
-                            <TextBlock x:Uid="AppTitleBarShutDown_Tooltip" />
-                        </ToolTip>
-                    </ToolTipService.ToolTip>
-                </Button>
-            </StackPanel>
         </Grid>
         <NavigationView
             x:Name="navigationView"
@@ -300,6 +275,11 @@
                         x:Uid="Feedback_NavViewItem"
                         Icon="{ui:FontIcon Glyph=&#xED15;}"
                         Tapped="FeedbackItem_Tapped" />
+                    <NavigationViewItem
+                        x:Uid="Close_NavViewItem"
+                        Icon="{ui:FontIcon Glyph=&#xE7E8;}"
+                        Tapped="Close_Tapped"
+                        Visibility="{x:Bind ViewModel.ShowCloseMenu, Mode=OneWay}" />
                 </StackPanel>
             </NavigationView.PaneFooter>
             <i:Interaction.Behaviors>
@@ -309,5 +289,12 @@
             </i:Interaction.Behaviors>
             <Frame x:Name="shellFrame" />
         </NavigationView>
+        <ContentDialog
+            x:Name="CloseDialog"
+            x:Uid="CloseDialog"
+            IsPrimaryButtonEnabled="True"
+            IsSecondaryButtonEnabled="True"
+            PrimaryButtonClick="CloseDialog_Click"
+            PrimaryButtonStyle="{StaticResource AccentButtonStyle}" />
     </Grid>
 </UserControl>