feat(game): add player cards and topbar styling for Chengdu Mahjong game
- Add new CSS classes for topbar layout including .topbar-left,
.topbar-back-btn, .topbar-room-meta, .eyebrow, and .topbar-room-name
- Create dedicated player card components for each seat position
(top, right, bottom, left)
- Refactor seatDecor computed property to use SeatPlayerCardModel
interface with proper typing
- Replace inline player badge rendering with reusable player card
components
- Update game header layout to use new topbar structure with
back button and room metadata
- Adjust spacing and font sizes in game header elements
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