XL landscape: revert tray to landscape style; fix sig-stage stretch

- Remove _tray.scss XL (≥1800px) portrait override block entirely
- _isLandscape() no longer returns false at ≥1800px — tray uses
  landscape slide-from-top at all wide landscape widths
- sig-stage: align-self: stretch (was center) so JS sizeSigCard()
  measures correct stage width; card size no longer collapses
- Position strip: horizontal row at top (was vertical column-reverse)
- sig-overlay/sig-stage/sig-deck-grid layout polish at 1100px/1800px

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

src/static_src/scss/_button-pad.scss

@@ -61,6 +61,13 @@
                 0 0 0.5rem rgba(var(--quaUser), 0.22)
             ;
         }
+
+        @media (orientation: landscape) and (max-width: 1100px) {
+            width: 2.75rem !important;
+            height: 2.75rem !important;
+            font-size: 0.625rem !important;
+            border-width: 0.125rem !important;
+        }
     }
 
     &.btn-abandon {