z-index audit + aperture fill + resize:end debounce + landscape sig-grid cap

- #id_aperture_fill: position:fixed→absolute (clips to .room-page, avoids h2/navbar);
  z-index 105→90 (below blur backdrops at z-100); landscape override removed (inset:0 works both orientations)
- _base.scss: landscape footer z-index:100 (matches navbar); corrects unset z-index
- _room.scss: fix stale "navbar z-300" comment; landscape sig-deck-grid columns
  repeat(9,1fr)→repeat(9,minmax(0,90px)) to cap card size on wide viewports
- room.js: add resize:end listeners for scaleTable + sizeSigModal; new IIFE dispatches
  resize:end 500ms after resize stops so both functions re-measure settled layout
- tray.js: extract _reposition() from inline resize handler; wire to both resize and
  resize:end so tray repositions correctly after rapid resize or orientation change

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/templates/apps/gameboard/room.html

@@ -7,6 +7,7 @@
 {% block content %}
     <div class="room-page" data-room-id="{{ room.id }}"
          {% if room.table_status %}data-select-role-url="{% url 'epic:select_role' room.id %}"{% endif %}>
+        <div id="id_aperture_fill"></div>
         <div class="room-shell">
             <div id="id_game_table" class="room-table">
                 {% if room.table_status == "ROLE_SELECT" %}