Add REST API endpoints for game lifecycle operations:
- POST /games - Create new game between two players
- GET /games/{game_id} - Get game info for reconnection
- GET /games/me/active - List user's active games
- POST /games/{game_id}/resign - Resign from game via HTTP
Includes proper reverse proxy support for WebSocket URL generation
(X-Forwarded-* headers -> settings.base_url -> Host header fallback).
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
