Phase 5: Complete Core Game Engine implementation

- Added MTGOnlineGame, GamePlayer, GameHistory models
- Implemented full game CRUD endpoints (create, list, get, join, leave, start, end)
- Integrated WebSocket game server with database persistence
- Added Commander deck validation service (100-card min, color identity, ban list)
- Created Alembic migration 006 for new game tables
- All game endpoints now database-backed (no more stubs)

backend/app/models/__init__.py

@@ -7,6 +7,7 @@ Consolidated from 10+ fragmented model files into 2 main modules:
 from app.models.models import (
     User, DecklistFile, DecklistFolder, Room, RoomGameType, Ban, GameLog, AuditLog,
     MtgonlineCard,
+    MTGOnlineGame, GamePlayer, GameHistory,
     UserDeck, UserDeckCard, DeckPrecedent, DeckPrecedentCard, CardSuggestion,
     UserSession, DeckVersion, GameReplay, ReplayPlayer, GameOutcome,
     UserStatistics, UserCardCollection, CardWishlist,
@@ -27,4 +28,5 @@ __all__ = [
     "UserActivityLog", "UserDeck", "UserDeckCard", "DeckPrecedent",
     "DeckPrecedentCard", "CardSuggestion", "CardImportBatch",
     "UserCardImportRecord", "UserCardImport",
+    "MTGOnlineGame", "GamePlayer", "GameHistory",
 ]