Fix missing-assets detection race, 16 KB page alignment, and Android audio backend

- QuestShockActivity now actually blocks the native engine from starting
  when game data is missing, closing three gaps found via on-device
  testing: super.onCreate() must run unconditionally first (Android
  throws SuperNotCalledException otherwise); SDLActivity.mBrokenLibraries
  is now set provisionally before the storage-permission check, since
  onWindowFocusChanged() closing the permission dialog could otherwise
  start the engine before the async onRequestPermissionsResult() callback
  ran; and a new GameSurface (SDLSurface subclass) closes the actual gap
  that let the init_popups NULL-deref crash through even with
  mBrokenLibraries set - SDLSurface.surfaceChanged() starts the native
  thread directly without ever checking that flag.
- Force Android to use SDL2's openslES audio backend instead of AAudio
  (android/engine-patches/05-android-audio-driver.patch): AAudio only
  allows one open playback device at a time, but the engine opens two
  (cutscene audio via SDL_OpenAudioDevice, SFX/MIDI via Mix_OpenAudio),
  hitting an assertion failure on real hardware.
- Add 16 KB ELF page-size alignment (-Wl,-z,max-page-size=16384) to every
  Android shared library - the four prebuilts (SDL2, SDL2_mixer,
  fluidsynth-lite, gl4es, in build-image/Dockerfile) and the engine's own
  libmain.so (build.gradle) - matching Google's Play Store requirement
  for Android 15+ and clearing Android Studio's compatibility warning.
- Add a stageEngine Gradle task that automatically re-stages the patched
  engine/ copy and prebuilt libraries before any Android Studio build
  (hooked into preBuild, with proper up-to-date checking), so source/
  patch changes can't silently go stale in the build/android-engine
  scratch copy - previously a manual, easy-to-forget step. Skips
  automatically inside the build-image container so make apk/CI are
  unaffected.

android/engine-patches/05-android-audio-driver.patch

@@ -0,0 +1,20 @@
+--- a/src/MacSrc/Shock.c
++++ b/src/MacSrc/Shock.c
+@@ -162,6 +162,17 @@
+ void InitSDL() {
+     SDL_SetHint(SDL_HINT_NO_SIGNAL_HANDLERS, "1");
+     SDL_SetHint(SDL_HINT_RENDER_DRIVER, "opengl");
++#ifdef __ANDROID__
++    // SDL2 2.28.5's AAudio backend (Android's default since API 26) only
++    // ever allows one open non-capture (playback) device at a time - it
++    // keeps a single static handle and asserts on a second open
++    // ('SDL_assert((audioDevice == NULL) || iscapture)' in
++    // src/audio/aaudio/SDL_aaudio.c). SDLSound.c opens two: one directly via
++    // SDL_OpenAudioDevice() for cutscene audio, one via Mix_OpenAudio() for
++    // SFX/MIDI. The older OpenSL ES backend has no such limitation, so force
++    // it instead of AAudio.
++    SDL_SetHint(SDL_HINT_AUDIODRIVER, "openslES");
++#endif
+     if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_AUDIO) < 0) {
+         DEBUG("%s: Init failed", __FUNCTION__);
+     }