fixed back button with source, and customer in customer lsit clickable

frontend/src/pages/contracts/ContractCockpit.tsx

@@ -282,7 +282,7 @@ export default function ContractCockpit() {
             <div className="flex items-center gap-2 flex-wrap">
               <Link
                 to={`/contracts/${contract.id}`}
-                state={{ from: 'cockpit', filter: filter !== 'all' ? filter : undefined }}
+                state={{ from: '/contracts/cockpit' }}
                 className="font-medium hover:underline"
                 onClick={(e) => e.stopPropagation()}
               >
@@ -399,7 +399,7 @@ export default function ContractCockpit() {
 
             <Link
               to={`/contracts/${contract.id}`}
-              state={{ from: 'cockpit', filter: filter !== 'all' ? filter : undefined }}
+              state={{ from: '/contracts/cockpit' }}
               className="p-2 hover:bg-white hover:bg-opacity-50 rounded"
               onClick={(e) => e.stopPropagation()}
               title="Zum Vertrag"