XL landscape breakpoint (≥1800px): double sidebar widths + scale content

- _base.scss: new @media (orientation:landscape) and (min-width:1800px) block —
  sidebars 4rem→8rem; navbar btn 3rem→5rem; brand h1 1.2rem→2.4rem; navbar-text
  0.65rem→1.3rem; footer icons 1.75rem→3rem; nav gap 3rem→4rem; footer-container
  0.55rem→0.85rem; container margins 4rem→8rem; h2 portrait-style (2rem, centred)
- _applets.scss: gear btn right 0.5rem→2.5rem; menus right 0.5rem→2rem at ≥1800px
- _game-kit.scss: kit btn right 0.5rem→2.5rem at ≥1800px
- _room.scss: sig-overlay padding-left 4rem→8rem at ≥1800px
- _tray.scss: tray wrap left/right 4rem→8rem at ≥1800px
- room.js: sizeSigModal right inset 64px→128px at ≥1800px viewport width

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

src/static_src/scss/_applets.scss

@@ -110,6 +110,7 @@
 }
 
 // In landscape: shift gear btn and applet menus left of the footer right sidebar
+// XL override below doubles sidebar to 8rem — centre items in the wider column.
 @media (orientation: landscape) {
     $sidebar-w: 4rem;
 
@@ -137,6 +138,24 @@
     }
 }
 
+@media (orientation: landscape) and (min-width: 1800px) {
+    // Centre gear btn and menus in the doubled 8rem sidebar (was 0.5rem from right edge)
+    .gameboard-page,
+    .dashboard-page,
+    .wallet-page,
+    .room-page,
+    .billboard-page {
+        > .gear-btn { right: 2.5rem; }
+    }
+
+    #id_dash_applet_menu,
+    #id_game_applet_menu,
+    #id_game_kit_menu,
+    #id_wallet_applet_menu,
+    #id_room_menu,
+    #id_billboard_applet_menu { right: 2rem; }
+}
+
 // ── Applet box visual shell (reusable outside the grid) ────
 %applet-box {
     border: