fix: use wl-copy for clipboard writes on native Wayland sessions

[jb0421]

Summary

Fixes #12534

On native Wayland sessions, QApplication::clipboard()->setText() is silently
dropped by the compositor when the ownCloud daemon has no focused surface — which
is always the case when the command arrives via the socket from a file manager
shell integration.

This change detects a native Wayland session via WAYLAND_DISPLAY and delegates
the clipboard write to wl-copy(1), which uses the Wayland primary selection
protocol and does not require a compositor surface.

Changes

• copyUrlToClipboard(): fall back to wl-copy when WAYLAND_DISPLAY is set
• Add #include <QProcess>
• Add changelog entry for COPY_PRIVATE_LINK and COPY_PUBLIC_LINK silently fail on native Wayland sessions #12534

Testing

Tested manually on Ubuntu 24.04 LTS (GNOME Wayland, Nautilus 46.4) with a locally
built client:

• Before: right-click → "Copy private link" → clipboard empty
• After: right-click → "Copy private link" → URL correctly pasted

Notes

wl-copy is provided by the wl-clipboard package, which is available on all
major Linux distributions and is a common dependency for Wayland clipboard tools.
If wl-copy is not installed, QProcess::startDetached silently fails and the
clipboard write is lost — same behaviour as before this fix.

See also: owncloud/client-desktop-shell-integration-nautilus#11 (comment)

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[DeepDiver1975]

Interesting approach indeed ..... requires wl-copy to be installed .... also needs to be ltested with the appimage - I guess we would need wl-copy to be packaged into the app image ...

[jb0421]

@DeepDiver1975 Should I create a new PR with wl-clipboard packaged into the AppImage, or do you as a Maintainer want to take over from here?

[DeepDiver1975]

Should I create a new PR with wl-clipboard packaged into the AppImage

feel free to give it a shot - thank you