Dashboard Studio 2.0.0: Admin, Builder and Dashboard screens, roles, Haven

- Home Assistant administrators are admins: Dashboard, Builder and Admin screens
- Everyone else only sees the dashboards an admin chose, always in kiosk mode;
  the server enforces it (saving, people, devices, history are admin-only, and
  the websocket only allows reading states and controlling devices)
- Admin screen: dashboards, people and what each sees (with preview), devices,
  messages to the screens, the Haven app, activity, about
- Haven: new Android app (haven/) that only shows dashboards; replaces the
  Dashboard Studio Android app and signs in through Home Assistant's page
- Screens pick up dashboard and access changes within a minute
- Version history records who made each change; panel visible to all users

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

haven/res/drawable/loading.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@drawable/ic_bg" />
+    <item android:gravity="center" android:width="160dp" android:height="160dp" android:drawable="@drawable/ic_fg" />
+</layer-list>