Add configurable game/initial screen width and distance, with a bundled first-run config

- Video Options tab offers width and distance presets independently for
  the Initial Screen (splash/intro/menu) and Game Screen (gameplay)
  profiles, with their preset step/offset configurable via
  questshock.config.json.
- Ships res/questshock.config.default.json as the initial config on
  first run (or whenever questshock.config.json doesn't exist yet),
  refreshed from the APK on every launch without touching a user's own
  saved config.

build-image/prepare-android-project.sh

@@ -81,7 +81,7 @@ fi
     echo "prebuiltDir=$PREBUILT_DIR_PROP"
 } > "$ANDROID_DIR/engine.properties"
 
-echo "== Staging bundled assets (shaders, soundfont, get-assets text) =="
+echo "== Staging bundled assets (shaders, soundfont, get-assets text, default config) =="
 ASSETS_DIR="$ANDROID_DIR/app/src/main/assets"
 rm -rf "$ASSETS_DIR"
 mkdir -p "$ASSETS_DIR/shaders" "$ASSETS_DIR/res"
@@ -91,6 +91,7 @@ mkdir -p "$ASSETS_DIR/shaders" "$ASSETS_DIR/res"
 cp -a "$ANDROID_DIR/gles-shaders/." "$ASSETS_DIR/shaders/"
 cp "/opt/prebuilt/soundfont/default.sf2" "$ASSETS_DIR/res/soundfont.sf2"
 cp "$REPO_ROOT/res/assets/GET_ASSETS_QUEST.txt" "$ASSETS_DIR/GET_ASSETS_QUEST.txt"
+cp "$REPO_ROOT/res/questshock.config.default.json" "$ASSETS_DIR/questshock.config.default.json"
 
 echo "== Staging prebuilt Android SDL2/SDL2_mixer/fluidsynth-lite/openxr .so's into jniLibs =="
 # gl4es is deliberately absent here - it's no longer prebuilt, it's compiled