FIX: Add right-click context menu to search entry

[carsteneu]

Fixes #13416

The menu search field didn't support right-click copy/paste. Users could only paste with Ctrl+V keyboard shortcut.

Added CinnamonEntry.addContextMenu() to the search entry, enabling the standard right-click context menu with copy/paste/select all options.

[fredcw]

This doesn't seem to work well for me. When I click paste, the applet just closes. And copy seems always greyed out even if there's text in the search entry.

[carsteneu]

Thank you very much @fredcw for testing and the valuable feedback!

I've updated the PR to fix the issues you reported:

What's fixed:

Clicking "Paste" no longer closes the menu - it now works as expected. I tested before, but I think I only checked that the context menu appeared, not the actual paste action. My apologies for that oversight!
Hover highlighting on menu items now works properly. This turned out to be quite complex to achieve - I found no other way than implementing it manually with mouse position polling.
A note on "Copy" being greyed out:
I believe this is the expected behavior - "Copy" should only be enabled when text is selected in the search field. Without a selection, there's nothing to copy. Similarly, "Paste" is only active when there's something in the clipboard.

Technical details:
The fix required extending the MenuManager's event handling to treat the context menu as part of the active menu, plus a manual hover implementation since the MenuManager blocks normal hover events.

Please test again when you have a chance - I really appreciate your help!

[fredcw]

This works well now.