feat: Add device-specific isolation for player IDs

- Add device ID generation (unique per device, stored in localStorage)
- Extend player ID format to: {basePlayerId}:{deviceId}
- Enable cross-domain sync on same device while keeping devices isolated
- Update backend APIs to support new player ID format
- Maintain backward compatibility with legacy UUID format

This allows:
- Each device (Desktop, Android, iOS) to have separate game states
- Cross-domain sync still works on the same device (hoerdle.de ↔ hördle.de)
- Easier debugging with visible device ID in player identifier

lib/playerStorage.ts

@@ -101,7 +101,9 @@ export async function savePlayerState(
     statistics: Statistics
 ): Promise<void> {
     try {
-        const playerId = getOrCreatePlayerId();
+        // Use async version to ensure device ID is included
+        const { getOrCreatePlayerIdAsync } = await import('./playerId');
+        const playerId = await getOrCreatePlayerIdAsync();
         if (!playerId) {
             console.warn('[playerStorage] No player ID available, cannot save state');
             return;