Dashboard Studio 1.7.0: scroll and swipe cards, more themes, per-device dashboards

- Container cards: horizontal scroll (snap, arrows, keeps position) and
  swipe (dots, optional autoplay that survives redraws and respects
  reduced motion), with add/edit/reorder of the cards inside
- Nine new themes, contrast-checked, including High contrast; bright
  accents get dark text
- Choose which dashboard opens per device (optionally in kiosk mode)
  and per Home Assistant user, via /api/whoami and the ingress user
  headers

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

dashboard_studio/web/index.html

@@ -36,6 +36,7 @@
         <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="assign" data-icon="person" data-i18n>Who sees which dashboard…</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>