feat: Remove localStorage for game states and implement cross-domain player ID sync

- Remove localStorage for game states and statistics (backend only)
- Add API route to suggest player ID based on recently updated states
- Add async player ID lookup that finds existing IDs across domains
- When visiting a new domain, automatically find and use existing player ID
- Enables cross-domain synchronization between hoerdle.de and hördle.de

lib/playerStorage.ts

@@ -37,7 +37,9 @@ export async function loadPlayerState(
     genreKey: string
 ): Promise<{ gameState: GameState; statistics: Statistics } | null> {
     try {
-        const playerId = getOrCreatePlayerId();
+        // Use async version to enable cross-domain player ID sync
+        const { getOrCreatePlayerIdAsync } = await import('./playerId');
+        const playerId = await getOrCreatePlayerIdAsync(genreKey);
         if (!playerId) {
             return null;
         }