fix(types): resolve TypeScript compilation errors in frontend build

frontend/src/features/lists/SharedListsView.tsx

@@ -529,6 +529,8 @@ export const SharedListsView: React.FC<SharedListsViewProps> = ({ onRefreshGloba
             const isShared =
               (activeSpace.shares && activeSpace.shares.length > 0) ||
               (activeSpace.members && activeSpace.members.length > 1);
+            const ownerMember = activeSpace.members?.find((m) => m.role === 'owner' || m.userId === activeSpace.ownerId);
+            const ownerDisplayName = activeSpace.ownerName || ownerMember?.displayName || ownerMember?.email || 'Eigentümer';
 
             return (
               <div className="flex items-center gap-1.5">
@@ -551,7 +553,7 @@ export const SharedListsView: React.FC<SharedListsViewProps> = ({ onRefreshGloba
                       title="Teilen & Berechtigungen öffnen"
                     >
                       <Users className="w-2.5 h-2.5" />
-                      <span>Geteilt von {activeSpace.ownerName || 'Eigentümer'}</span>
+                      <span>Geteilt von {ownerDisplayName}</span>
                     </button>
                   )
                 )}