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/translations/main_fr.ts

@@ -814,15 +814,15 @@
     <name>OffroadHome</name>
     <message>
         <source>UPDATE</source>
-        <translation>MISE À JOUR</translation>
+        <translation type="vanished">MISE À JOUR</translation>
     </message>
     <message>
         <source> ALERTS</source>
-        <translation> ALERTES</translation>
+        <translation type="vanished"> ALERTES</translation>
     </message>
     <message>
         <source> ALERT</source>
-        <translation> ALERTE</translation>
+        <translation type="vanished"> ALERTE</translation>
     </message>
 </context>
 <context>