feat(android): close behaviour gaps between the APK and the browser

Several behaviours diverged between the web build and the Capacitor
wrapper, none of them reproducible on a desktop browser.

- Declare VIBRATE. PlayerBoard calls navigator.vibrate() on every cell
  tap; a WebView app must hold the permission itself, where a browser
  holds it on the page's behalf. Taps were silent in the APK.
- Hold a screen wake lock while numbers remain to be called. Auto-call
  advances on a timer with no touch input, so a round could run 15
  minutes untouched — long enough for the display to sleep and the
  WebView to throttle the interval. Android drops the lock whenever the
  page hides, so wake-lock.js re-acquires on visibilitychange.
- Handle back through OnBackPressedCallback. Android 16 (targetSdk 36)
  no longer calls onBackPressed() nor dispatches KEYCODE_BACK. Each open
  overlay pushes one history entry, so "the WebView can go back" means
  "an overlay is open": back closes the bingo modal or settings sheet,
  and only at the root does it confirm before quitting. Browsers get the
  overlay behaviour too.
- Inset content by env(safe-area-inset-*) with viewport-fit=cover.
  targetSdk 36 forces edge-to-edge, so the WebView painted under the
  status bar and gesture nav. Also fixes the iOS PWA notch.
- Pin the WebView's textZoom to 100 and add a "Cỡ chữ bảng" setting.
  The player card is a fixed 9-column grid that clips at large system
  font scales. Pinning the zoom overrides an accessibility control, so
  the app now owns an equivalent one; the two belong together.
- Point the volume rocker at the media stream, so it works before the
  first clip plays.

strings.xml also gains the exit-dialog strings and picks up the
diacritics in app_name.

android/android/app/src/main/AndroidManifest.xml

@@ -3,6 +3,7 @@
 
     <application
         android:allowBackup="true"
+        android:enableOnBackInvokedCallback="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:roundIcon="@mipmap/ic_launcher_round"
@@ -38,6 +39,12 @@
     <!-- No INTERNET permission: app is fully offline. All assets bundled in
          APK; WebView serves from https://localhost which uses loopback. -->
 
+    <!-- Haptic feedback on cell taps. A WebView app must declare this itself
+         for navigator.vibrate() to work — Chrome holds the permission on the
+         browser's behalf, which is why the web build needs no equivalent.
+         Normal permission: no runtime prompt, no data-safety impact. -->
+    <uses-permission android:name="android.permission.VIBRATE" />
+
     <!-- Mark hardware as optional so emulators (BlueStacks, NoxPlayer, AVDs)
          don't get filtered out. BlueStacks reports `faketouch` instead of
          `touchscreen` and lacks real telephony/GPS hardware. -->

android/android/app/src/main/java/com/miti99/loto/MainActivity.java

@@ -1,5 +1,74 @@
 package com.miti99.loto;
 
+import android.media.AudioManager;
+import android.os.Bundle;
+import android.webkit.WebView;
+import androidx.activity.OnBackPressedCallback;
+import androidx.appcompat.app.AlertDialog;
+import com.getcapacitor.Bridge;
 import com.getcapacitor.BridgeActivity;
 
-public class MainActivity extends BridgeActivity {}
+public class MainActivity extends BridgeActivity {
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        WebView webView = webView();
+        if (webView != null) {
+            // The player card is a fixed 9-column grid, so the system font
+            // scale (users routinely run 130-200%) clips two-digit numbers
+            // out of their cells. Pinning the zoom is only defensible
+            // because the app ships its own size control in Settings
+            // ("Cỡ chữ bảng") as the accessible replacement.
+            webView.getSettings().setTextZoom(100);
+        }
+
+        // Calling numbers aloud is the app's whole job, so the volume rocker
+        // should reach the media stream even before the first clip plays.
+        setVolumeControlStream(AudioManager.STREAM_MUSIC);
+
+        // Android 16 (targetSdk 36) no longer calls onBackPressed() and no
+        // longer dispatches KEYCODE_BACK, so back has to come through the
+        // dispatcher. Each open overlay pushes one history entry (see
+        // web/src/lib/overlay-history.js), which makes "the WebView can go
+        // back" mean exactly "an overlay is open".
+        getOnBackPressedDispatcher()
+            .addCallback(
+                this,
+                new OnBackPressedCallback(true) {
+                    @Override
+                    public void handleOnBackPressed() {
+                        WebView wv = webView();
+                        if (wv != null && wv.canGoBack()) {
+                            wv.goBack();
+                            return;
+                        }
+                        confirmExit();
+                    }
+                }
+            );
+    }
+
+    /** Null-safe accessor — the bridge is built during super.onCreate(). */
+    private WebView webView() {
+        Bridge bridge = getBridge();
+        return bridge == null ? null : bridge.getWebView();
+    }
+
+    /**
+     * Auto-call runs untouched for minutes at a time, so a stray back press
+     * at the root would otherwise drop the caller out of a live round.
+     */
+    private void confirmExit() {
+        // Explicit AppCompat dialog theme: the activity runs on
+        // AppTheme.NoActionBarLaunch (parent Theme.SplashScreen), which is
+        // not guaranteed to be AppCompat-derived at dialog time.
+        new AlertDialog.Builder(this, R.style.AppTheme_ExitDialog)
+            .setTitle(R.string.exit_title)
+            .setMessage(R.string.exit_message)
+            .setNegativeButton(R.string.exit_cancel, null)
+            .setPositiveButton(R.string.exit_confirm, (dialog, which) -> finish())
+            .show();
+    }
+}

android/android/app/src/main/res/values/strings.xml

@@ -1,7 +1,13 @@
 <?xml version='1.0' encoding='utf-8'?>
 <resources>
-    <string name="app_name">Lo To</string>
-    <string name="title_activity_main">Lo To</string>
+    <string name="app_name">Lô tô</string>
+    <string name="title_activity_main">Lô tô</string>
     <string name="package_name">com.miti99.loto</string>
     <string name="custom_url_scheme">com.miti99.loto</string>
+
+    <!-- Exit confirmation, shown when back is pressed with no overlay open. -->
+    <string name="exit_title">Thoát Lô tô?</string>
+    <string name="exit_message">Ván đang chơi sẽ được lưu lại.</string>
+    <string name="exit_confirm">Thoát</string>
+    <string name="exit_cancel">Ở lại</string>
 </resources>

android/android/app/src/main/res/values/styles.xml

@@ -17,6 +17,21 @@
 
 
     <style name="AppTheme.NoActionBarLaunch" parent="Theme.SplashScreen">
+        <!-- API 31+ system splash. Colour follows light/dark via
+             values-night/colors.xml. -->
+        <item name="windowSplashScreenBackground">@color/splash_background</item>
+        <item name="windowSplashScreenAnimatedIcon">@mipmap/ic_launcher_foreground</item>
+        <!-- Hand the activity a normal AppCompat theme once the splash is
+             done; Theme.SplashScreen is not meant to stay applied, and
+             AppCompat dialogs need an AppCompat-derived theme. -->
+        <item name="postSplashScreenTheme">@style/AppTheme.NoActionBar</item>
+        <!-- Compat path for API < 31; see drawable/splash.xml. -->
         <item name="android:background">@drawable/splash</item>
     </style>
+
+    <!-- Exit-confirmation dialog. Declared with an explicit AppCompat parent
+         because the activity theme (Theme.SplashScreen) is not guaranteed to
+         be AppCompat-derived, and AppCompat's AlertDialog requires one.
+         DayNight so the dialog follows the app's light/dark setting. -->
+    <style name="AppTheme.ExitDialog" parent="Theme.AppCompat.DayNight.Dialog.Alert" />
 </resources>