feat(shop): reset customer on partner change and enforce customer selection

shop/components/wizard/step-customer.tsx

@@ -202,7 +202,10 @@ export function StepCustomer({
             <div className="space-y-2 max-h-72 overflow-y-auto pr-1">
               {/* Reserved Fixed Card: Alle Partner */}
               <div
-                onClick={() => setSelectedCompanyId('all')}
+                onClick={() => {
+                  setSelectedCompanyId('all')
+                  setSelectedEndCustomerId(null)
+                }}
                 className={`flex items-center justify-between p-3.5 rounded-xl border-2 cursor-pointer transition-all select-none ${
                   selectedCompanyId === 'all' || !selectedCompanyId
                     ? 'border-primary bg-primary/10 shadow-lg shadow-primary/5'
@@ -240,7 +243,10 @@ export function StepCustomer({
                 return (
                   <div
                     key={c.id}
-                    onClick={() => setSelectedCompanyId(c.id)}
+                    onClick={() => {
+                      setSelectedCompanyId(c.id)
+                      setSelectedEndCustomerId(null)
+                    }}
                     className={`flex items-center justify-between p-3.5 rounded-xl border-2 cursor-pointer transition-all select-none ${
                       isSelected
                         ? 'border-primary bg-primary/10 shadow-lg shadow-primary/5'
@@ -592,9 +598,7 @@ export function StepCustomer({
           onClick={nextStep}
           disabled={
             customerMode === 'create' ||
-            (customerMode === 'select' &&
-              customersByCompany.length > 0 &&
-              !selectedEndCustomerId)
+            !selectedEndCustomerId
           }
         >
           Weiter zum Abrechnungsmodell <ChevronRight className="ml-2 w-4 h-4" />