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>

dashboard_studio/web/index.html

@@ -40,24 +40,19 @@
         <button id="btn-guest" class="btn view-only" hidden><span data-i18n>Guest mode</span></button>
         <button id="btn-app" class="btn icon view-only" aria-label="Install as an app" title="Install as an app"></button>
         <button id="btn-kiosk" class="btn view-only label-wide" aria-label="Kiosk" title="Kiosk mode"><span data-i18n>Kiosk</span></button>
-        <button id="btn-edit" class="btn primary" data-i18n>Edit</button>
+        <div id="mode-seg" class="mode-seg" role="tablist" aria-label="Screen" hidden>
+          <button role="tab" data-mode="dashboard" data-icon="layout"><span data-i18n>Dashboard</span></button>
+          <button role="tab" data-mode="builder" data-icon="edit"><span data-i18n>Builder</span></button>
+          <button role="tab" data-mode="admin" data-icon="shield"><span data-i18n>Admin</span></button>
+        </div>
       </div>
       <div id="menu" class="menu" role="menu" hidden>
         <button role="menuitem" data-menu="rename" data-icon="edit" data-i18n>Rename…</button>
-        <button role="menuitem" data-menu="duplicate" data-icon="copy" data-i18n>Duplicate</button>
-        <button role="menuitem" data-menu="starter" data-icon="sparkles" data-i18n>New dashboard from my devices</button>
         <button role="menuitem" data-menu="suggest" data-icon="search" data-i18n>Devices not on a dashboard…</button>
-        <button role="menuitem" data-menu="assign" data-icon="person" data-i18n>Who sees which dashboard…</button>
         <button role="menuitem" data-menu="history" data-icon="history" data-i18n>Version history…</button>
         <button role="menuitem" data-menu="undo-history" data-icon="undo" data-i18n>Undo history…</button>
         <button role="menuitem" data-menu="share" data-icon="share" data-i18n>Share…</button>
-        <button role="menuitem" data-menu="install" data-icon="phone" data-i18n>Install as an app…</button>
-        <hr>
         <button role="menuitem" data-menu="export" data-icon="exit" data-i18n>Export as JSON</button>
-        <button role="menuitem" data-menu="import" data-icon="plus" data-i18n>Import JSON…</button>
-        <button role="menuitem" data-menu="lovelace" data-icon="import" data-i18n>Import from Home Assistant…</button>
-        <hr>
-        <button role="menuitem" data-menu="delete" data-icon="trash" class="danger" data-i18n>Delete dashboard…</button>
       </div>
     </header>
 
@@ -77,6 +72,12 @@
 
       <aside id="inspector" class="edit-only" aria-label="Inspector"></aside>
     </div>
+
+    <!-- Admin: dashboards, people, devices, the Haven app, activity -->
+    <section id="admin" hidden aria-label="Admin">
+      <nav class="adm-nav" role="tablist" aria-label="Admin"></nav>
+      <div class="adm-body"></div>
+    </section>
   </div>
 
   <div id="edit-bar" class="edit-only"><button class="btn" id="eb-add"><span data-i18n>Add</span></button><button class="btn primary" id="eb-insp"></button></div>
@@ -84,6 +85,8 @@
   <div id="saver" hidden aria-hidden="true"><div class="photos"><img class="ph-layer" alt=""><img class="ph-layer" alt=""><div class="ph-msg"></div></div><div class="saver-clock"><div class="time num"></div><div class="date"></div></div></div>
   <div id="doorbell" hidden role="alertdialog" aria-modal="true" aria-labelledby="db-title"><div class="db-cam"></div><div class="db-bar"><div class="db-title" id="db-title"></div><button class="btn db-close">Close</button></div></div>
   <div id="night-dim" aria-hidden="true"></div>
+  <div id="preview-bar" hidden role="status"><span class="pv-text"></span><button class="btn" id="pv-stop"><span data-i18n>Stop preview</span></button></div>
+  <div id="empty-note" hidden role="status"><div class="en-card"><div class="en-ico"></div><h2 data-i18n>Nothing to show yet</h2><p class="en-text"></p></div></div>
   <button id="phone-menu" class="btn icon" aria-label="Menu" title="Menu"></button>
   <div id="offline-note" hidden role="status"></div>
   <div id="ptr" hidden aria-hidden="true"><svg viewBox="0 0 24 24"><path d="M20 11a8 8 0 1 0-2.3 5.7M20 4v7h-7"/></svg></div>