fix(backup): include psysonic_home in backup keys

Home section visibility/order is a user preference and was missing
from the backup. Server-specific stores (offline, playlists_recent)
intentionally excluded.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/utils/backup.ts

@@ -14,6 +14,7 @@ const BACKUP_KEYS = [
   'psysonic-eq',
   'psysonic_global_shortcuts',
   'psysonic-player',
+  'psysonic_home',
 ];
 
 export async function exportBackup(): Promise<string | null> {