Issue #206: Fix AppBarLayout insets.

We're hitting this behavior change when targeting Android 15: https://developer.android.com/about/versions/15/behavior-changes-15#not-edge-to-edge

The documentation says:
> you need to add android:fitsSystemWindows="true" if using AppBarLayout.

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

@@ -35,6 +35,7 @@
             android:id="@+id/app_bar_layout"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:fitsSystemWindows="true"
             android:theme="@style/AppTheme.AppBarOverlay">
 
             <androidx.appcompat.widget.Toolbar