Release 0.2.43 and Quest app 0.4.0

Bump the backend to 0.2.43 and the Quest app to versionCode 4 / 0.4.0-quest
for the release that brings heurazy's cockpit and hand steering, and the
flat-screen mode and camera switching Darthcircuit suggested.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/app/build.gradle.kts

@@ -100,8 +100,8 @@ android {
         // Quest 2 ships Android 10 (API 29); AHardwareBuffer/Vulkan 1.1 need 26+.
         minSdk = 29
         targetSdk = 34
-        versionCode = 3
-        versionName = "0.3.0-quest"
+        versionCode = 4
+        versionName = "0.4.0-quest"
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
 
         for ((name, value) in discPins) {