feat(chess): complete pro features — premoves, rating graph, puzzle themes, best move comparison, opening explorer

NEW MODULES:
- premove.js: Queue moves during opponent's turn, auto-execute when legal
- rating-graph.js: Canvas sparkline with gradient fill, grid, current rating label, change indicator
- themes.js: 16 puzzle themes with Arabic names and icons for filtering
- analyzer.js: Full game analysis — classifies every move, calculates accuracy per game
- explorer.js: Opening explorer database — popular moves with white/draw/black win rates + visual bar

ANALYSIS SCENE UPGRADED:
- Shows opening explorer data (book moves + win rate bars) above engine analysis
- Engine lines show best moves with eval and principal variation
- Move navigator with clickable chips

GAME SCENE UPGRADED:
- Opening name shown in Arabic during game (40+ ECO openings)
- Material advantage displayed (+2/-1) with color coding
- PGN share/copy buttons on result screen
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>