🐛 pin footer menu items to prevent scrolling

[keeleycenc]

Pull request type

Please check the type of change your PR introduces:

• Update
• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes

What is the current behavior?

In LeftNavigationViewTemplate:

• at the bottom of the menu item (PART_FooterMenuItemsItemsControl) nested within DynamicScrollViewer, with the main course of a single scroll
• It does not meet users' interaction expectations for fixed bottom menus (such as Settings/exit buttons)
• Visually, there is a lack of a separation line between the menu area and the bottom

What is the new behavior?

LeftNavigationViewTemplate changes:

• The bottom menu is now fixed and not affected by the scrolling of the main menu
• New dividing lines are added to clarify the visual hierarchy
• Structural adjustment：

<!-- Before -->
DynamicScrollViewer
  ├─ MenuItems
  └─ FooterItems

<!-- After -->
DynamicScrollViewer
Separator
Fixed FooterItems

Other information

• • The Footer is always fixed at the bottom, and the interaction is more in line with the specifications of modern navigation controls such as Windows 11

Scope of influence:

• Only affects usingLeftNavigationViewTemplateNavigationView instance

[huiyadanli]

The updated interface looks worse than before.

[keeleycenc]

The updated interface looks worse than before.更新后的界面看起来比以前更糟糕。

This is a horizontal linear gradient with a smooth transition for the divider. Admittedly, design is subjective—some favor clearer sectioning, while others prefer absolute, distraction - free simplicity. Your perspective is really important.

We’ll re - evaluate possible adjustments during future optimizations, such as considering an option to toggle the divider on or off.