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

On Wayland the ownCloud daemon has no compositor surface and never
receives keyboard focus, so QClipboard::setText() is silently dropped
by the compositor when COPY_PRIVATE_LINK is handled.

Detect a native Wayland session via WAYLAND_DISPLAY and delegate the
clipboard write to wl-copy(1), which does not require a compositor
surface.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: jb0421

changelog/unreleased/12534.md

@@ -0,0 +1,8 @@
+Bugfix: Fix "Copy private link to clipboard" on native Wayland sessions
+
+The "Copy private link to clipboard" action now correctly writes to the
+clipboard on native Wayland sessions. Previously the write was silently
+dropped by the Wayland compositor because the ownCloud daemon has no
+compositor surface.
+
+https://github.com/owncloud/client/issues/12534

src/gui/socketapi/socketapi.cpp

@@ -54,6 +54,7 @@
 #include <QBuffer>
 
 #include <QClipboard>
+#include <QProcess>
 
 #ifdef Q_OS_MAC
 #include <CoreFoundation/CoreFoundation.h>
@@ -672,7 +673,11 @@ void SocketApi::command_OPEN_PRIVATE_LINK_VERSIONS(const QString &localFile, Soc
 
 void SocketApi::copyUrlToClipboard(const QUrl &link)
 {
-    QApplication::clipboard()->setText(link.toString());
+    if (!qgetenv("WAYLAND_DISPLAY").isEmpty()) {
+        QProcess::startDetached(QStringLiteral("wl-copy"), {link.toString()});
+    } else {
+        QApplication::clipboard()->setText(link.toString());
+    }
 }
 
 void SocketApi::command_MAKE_AVAILABLE_LOCALLY(const QString &filesArg, SocketListener *)