fix: redesign backgammon game UI with real player data + polished visuals

- Player cards now use store player data (avatar_url, display_name, level)
- Opponent shows bot icon or opponent data for multiplayer
- Active turn highlight on player cards with green glow border
- Cube value display in match info area
- Professional dark gradient background with proper hierarchy
- Controls bar with proper spacing and button styling
- Doubling offer dialog with backdrop blur and better layout
- Turn badge repositioned to top-center with pill shape
- Emote panel centered with backdrop blur
- All interactive elements have proper touch targets (40px+)
- Safe area inset for bottom bar
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>