Problem 1: Reconnection reset board to starting position
- engine.create() always starts fresh
- FIX: if params.recovered, fetch match from server → engine.load(current_fen)
- Also restores clock times + determines whose turn from FEN

Problem 2: Opponent name stuck on 'جاري التحميل'
- params.opponentId was undefined (not passed on reconnect or matchmaking)
- FIX: if no opponentId in params, fetch match → get white/black_player_id → find opponent
- Uses fetchAndRenderOpponent() helper to update avatar/name/level

Problem 3: Other player can't see moves after reconnect
- This was because board reset to start position
- Now board loads current_fen from server → correct position displayed
- Polling continues from correct move_count
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>