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/app/build.gradle

@@ -0,0 +1,54 @@
+apply plugin: 'com.android.application'
+
+android {
+    namespace = "dev.ncode.sp404layers"
+    compileSdk = rootProject.ext.compileSdkVersion
+    defaultConfig {
+        applicationId "dev.ncode.sp404layers"
+        minSdkVersion rootProject.ext.minSdkVersion
+        targetSdkVersion rootProject.ext.targetSdkVersion
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+        aaptOptions {
+             // Files and dirs to omit from the packaged assets dir, modified to accommodate modern web apps.
+             // Default: https://android.googlesource.com/platform/frameworks/base/+/282e181b58cf72b6ca770dc7ca5f91f135444502/tools/aapt/AaptAssets.cpp#61
+            ignoreAssetsPattern = '!.svn:!.git:!.ds_store:!*.scc:.*:!CVS:!thumbs.db:!picasa.ini:!*~'
+        }
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+repositories {
+    flatDir{
+        dirs '../capacitor-cordova-android-plugins/src/main/libs', 'libs'
+    }
+}
+
+dependencies {
+    implementation fileTree(include: ['*.jar'], dir: 'libs')
+    implementation "androidx.appcompat:appcompat:$androidxAppCompatVersion"
+    implementation "androidx.coordinatorlayout:coordinatorlayout:$androidxCoordinatorLayoutVersion"
+    implementation "androidx.core:core-splashscreen:$coreSplashScreenVersion"
+    implementation project(':capacitor-android')
+    testImplementation "junit:junit:$junitVersion"
+    androidTestImplementation "androidx.test.ext:junit:$androidxJunitVersion"
+    androidTestImplementation "androidx.test.espresso:espresso-core:$androidxEspressoCoreVersion"
+    implementation project(':capacitor-cordova-android-plugins')
+}
+
+apply from: 'capacitor.build.gradle'
+
+try {
+    def servicesJSON = file('google-services.json')
+    if (servicesJSON.text) {
+        apply plugin: 'com.google.gms.google-services'
+    }
+} catch(Exception e) {
+    logger.info("google-services.json not found, google-services plugin not applied. Push Notifications won't work")
+}