Forward Tab/Shift+Tab to remote sessions instead of local focus navigation

QWidget's default handling intercepts Tab/Shift+Tab for focus-chain
navigation before they ever reach keyPressEvent(), so pressing Tab in an
RDP session moved focus to the OrbitHub UI (e.g. the Show Events button)
instead of reaching the remote machine. KodoTerm (SSH) already overrides
focusNextPrevChild() to opt out of this; RdpDisplayWidget and TerminalView
did not. Both already handle Key_Tab in their own keyPressEvent, so this
is enough to let it reach them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/rdp_display_widget.h

@@ -40,6 +40,7 @@ protected:
     void mouseReleaseEvent(QMouseEvent* event) override;
     void mouseMoveEvent(QMouseEvent* event) override;
     void wheelEvent(QWheelEvent* event) override;
+    bool focusNextPrevChild(bool next) override;
 
 private:
     enum class CursorMode {