feat(web): add multiplayer lobby, game, and score screen routes

- lobby.$code.tsx: waiting room with live player list via lobby:state,
  copyable lobby code, host Start Game button (disabled until 2+ players),
  sends lobby:join on connect, lobby:leave on unmount
- game.$code.tsx: in-game view, sends game:ready on mount to get current
  question, handles game:question/answer_result/finished messages,
  reuses QuestionCard component, shows round results after each answer
- MultiplayerScoreScreen: final score screen sorted by score, highlights
  winner(s) with crown, handles ties via winnerIds array, Play Again
  navigates back to lobby, Leave goes to multiplayer landing
- GameRouteSearchSchema added to shared for typed lobbyId search param
  without requiring Zod in apps/web

packages/shared/src/schemas/lobby.ts

@@ -27,6 +27,9 @@ export const JoinLobbyResponseSchema = LobbySchema;
 
 export type JoinLobbyResponse = z.infer<typeof JoinLobbyResponseSchema>;
 
+export const GameRouteSearchSchema = z.object({ lobbyId: z.uuid() });
+export type GameRouteSearch = z.infer<typeof GameRouteSearchSchema>;
+
 // ----------------------------------------------------------------------------
 // WebSocket: Client → Server
 // ----------------------------------------------------------------------------