refactor(tray): remove obsolete tray window

Signed-off-by: Rello <github@scherello.de>

Assisted-by: Codex:GPT-5

Author: Rello

resources.qrc

@@ -28,7 +28,6 @@
         <file>src/gui/filedetails/ShareDetailsPage.qml</file>
         <file>src/gui/filedetails/ShareeSearchField.qml</file>
         <file>src/gui/filedetails/ShareView.qml</file>
-        <file>src/gui/tray/MainWindow.qml</file>
         <file>src/gui/tray/UserLine.qml</file>
         <file>src/gui/tray/HeaderButton.qml</file>
         <file>src/gui/activity/qml/SyncStatus.qml</file>