landscape layout: remove max-width cutoff; sig-select stage/grid polish

- All landscape @media queries: drop and (max-width: 1440px) — sidebar layout
  now activates for all landscape orientations regardless of viewport width
- _base.scss landscape container: add max-width:none to override the
  @media(min-width:1200px) rule and fill the full space between sidebars
- sig-select sig-deck-grid: landscape now 9×2 @ 3rem cards; 18×1 at ≥1100px
  (bumped from 992px to avoid last-card clip); card text scales with --sig-card-w
- sig-stat-block: flex:1→flex:0 0 auto with width:--sig-card-w so it matches
  preview card dimensions instead of stretching across the full stage
- room.js sizeSigModal: landscape card width clamped to [90px, 160px]

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

src/static_src/scss/_base.scss

@@ -192,7 +192,7 @@ body {
     }
 }
 
-@media (orientation: landscape) and (max-width: 1440px) {
+@media (orientation: landscape) {
     $sidebar-w: 4rem;
 
     // ── Sidebar layout: navbar ← left, footer → right ────────────────────────────
@@ -288,10 +288,13 @@ body {
         }
     }
 
-    // Container: fill center, compensate for fixed sidebars on both sides
+    // Container: fill center, compensate for fixed sidebars on both sides.
+    // max-width: none overrides the @media (min-width: 1200px) rule above so the
+    // container fills all available space between the two sidebars on wide screens.
     body .container {
         flex: 1;
         min-width: 0;
+        max-width: none;
         margin-left: $sidebar-w;
         margin-right: $sidebar-w;
         padding: 0 0.5rem;