Fix: Scroll into view on keyboard navigation

[OmarAhmed-A]

Summary

This PR implements the "scroll into view" functionality when navigating the clipboard history using the keyboard (Up/Down or Left/Right arrows). Previously, the selection would move, but the list would not scroll to keep the selected item visible.

Changes

• src/view.rs: Assigned a unique SCROLLABLE_ID to the scrollable widgets in both horizontal and vertical layouts, allowing them to be targeted by the application logic.
• src/app.rs:
  • Updated focus_next and focus_previous to calculate the correct relative scroll offset based on the current page and item index.
  • Fixed the scroll clamping logic to ensure correct behavior.

Verification

• Verified that pressing the arrow keys now correctly scrolls the list to show the currently selected item.

This PR starts from #160