Move Hole indicator and End Game button to mobile bottom bar

- Add round info and leave button to mobile-bottom-bar HTML
- Hide .round-info and #leave-game-btn from header on mobile
- Style round info as subtle text, leave button as red-tinted pill
- Slim down bottom bar: smaller gaps/padding to fit 4 items
- Sync round numbers and leave text via JS (renderGame + bindEvents)
- Frees up header space, reduces mobile crowding

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

client/index.html

@@ -401,8 +401,10 @@
 
             <!-- Mobile bottom bar (hidden on desktop) -->
             <div id="mobile-bottom-bar">
+                <div class="mobile-round-info">Hole <span id="mobile-current-round">1</span>/<span id="mobile-total-rounds">9</span></div>
                 <button class="mobile-bar-btn" data-drawer="standings-panel">Standings</button>
                 <button class="mobile-bar-btn" data-drawer="scoreboard">Scores</button>
+                <button id="mobile-leave-btn" class="mobile-bar-btn mobile-leave-btn">End Game</button>
             </div>
 
             <!-- Drawer backdrop for mobile -->