Phase 1: wrap the reference web app in Capacitor for Android

Wraps reference/sp404-layers as a sideloadable APK without editing the
reference, which stays the frozen spec for the Phase 2 React port.

- sync-www.sh builds www/ from reference/ + native/, asserting each patch
  anchor so a reference change fails loudly rather than shipping broken
- drops the service worker (would serve a stale app after an APK update)
- haptics via a navigator.vibrate override, so buzz() needs no change
- localStorage mirrored into Preferences; sync load()/save() untouched
- hardware back: sheet -> Explore tab -> exit
- edge-to-edge handled in MainActivity: Android 16 + targetSdk 36 removes
  the opt-out, and a WebView never fills env(safe-area-inset-*), so insets
  are pushed into CSS custom properties instead

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

android/settings.gradle

@@ -0,0 +1,5 @@
+include ':app'
+include ':capacitor-cordova-android-plugins'
+project(':capacitor-cordova-android-plugins').projectDir = new File('./capacitor-cordova-android-plugins/')
+
+apply from: 'capacitor.settings.gradle'