offroad UI: replace stock home with clean grid launcher

- Strip out date, version, update/alert widgets from OffroadHome
- Replace with grid layout: Dashcam and Settings buttons
- Skip sidebar when tapping splash screen
- Settings button still opens original comma settings
- Dashcam button placeholder (viewer not yet built)
- Add DASHCAM_PROJECT.md with plans for footage viewer

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

selfdrive/ui/qt/home.h

@@ -24,24 +24,6 @@ public:
 
 signals:
   void openSettings(int index = 0, const QString &param = "");
-
-private:
-  void showEvent(QShowEvent *event) override;
-  void hideEvent(QHideEvent *event) override;
-  void refresh();
-
-  Params params;
-
-  QTimer* timer;
-  ElidedLabel* version;
-  QStackedLayout* center_layout;
-  UpdateAlert *update_widget;
-  OffroadAlert* alerts_widget;
-  QPushButton* alert_notif;
-  QPushButton* update_notif;
-
-  // FrogPilot variables
-  ElidedLabel* date;
 };
 
 class HomeWindow : public QWidget {