feat(chess): full gameplay polish — move list, captured pieces, promotion dialog, bot thinking indicator, clock urgency, improved result screen

- Move list: scrollable horizontal move notation (SAN)
- Captured pieces: sorted display below each player name
- Promotion dialog: visual piece picker (Q/R/B/N) instead of auto-queen
- Bot thinking indicator: animated dots overlay during Stockfish response
- Clock urgency: red pulsing animation when time < 30s
- Resign confirmation: prevents accidental resign
- Result screen: proper rating change, coins, XP, move history, analysis button
- Sound: differentiated for check, checkmate, castle, capture, normal move
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>