feat: MVP implementation - Kiosk Browser

- Fullscreen WebView with immersive mode
- URL whitelist system
- Admin PIN-protected settings
- Boot receiver for auto-launch
- Idle timeout with homepage reset
- Lock Task Mode support
- Material Design 3 UI

Team: Pluto (coordinator), Margaret, Spirit

app/src/main/res/layout/activity_main.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <WebView
+        android:id="@+id/webView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+    <!-- Invisible admin tap area (top-left corner) -->
+    <View
+        android:id="@+id/adminTapArea"
+        android:layout_width="80dp"
+        android:layout_height="80dp"
+        android:layout_gravity="start|top"
+        android:onClick="onAdminAreaTap" />
+
+</FrameLayout>