Mobile UI polish pass (game-ui-design + mobile-app-ui-design)

Grounded in the two installed design skills:
- Safe-area insets (notch/home-bar): .safe-top/.safe-bottom/.safe-x helpers
  applied to the game-table HUD + bottom hand + reaction button, and to
  ScreenShell + HomeScreen (covers Profile/Shop/Leaderboard/etc.).
- Touch targets ≥44px: table HUD buttons (mute/forfeit/exit) and the reaction
  button now meet the 44/48px minimum.
- HUD readability: seat name/level labels (which float over the felt) get a
  text-shadow (.hud-shadow) and stronger contrast.

Verified: tsc + next build clean; web image rebuilt on :1500.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/globals.css

@@ -59,6 +59,19 @@
   box-shadow: 0 0 10px rgba(212, 175, 55, 0.45);
 }
 
+/* HUD text stays legible over the dynamic felt/table (game-ui best practice). */
+.hud-shadow {
+  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.6), 0 0 6px rgba(0, 0, 0, 0.4);
+}
+
+/* Safe-area helpers for notch / home-indicator on phones. */
+.safe-top { padding-top: max(0.75rem, env(safe-area-inset-top)); }
+.safe-bottom { padding-bottom: max(0.5rem, env(safe-area-inset-bottom)); }
+.safe-x {
+  padding-left: max(0.75rem, env(safe-area-inset-left));
+  padding-right: max(0.75rem, env(safe-area-inset-right));
+}
+
 html,
 body {
   height: 100%;