fix(wizard): make last license date optional in step 2

shop/components/wizard/step-billing.tsx

@@ -40,9 +40,6 @@ export function StepBilling({
   const isOneTime = selectedBillingInterval === 'one_time'
   const isMonthly = selectedBillingInterval === 'monthly'
 
-  // Wenn Kauf gewählt ist, muss ein gültiges Datum vorliegen
-  const isNextDisabled = isOneTime && !lastLicenseDate
-
   return (
     <Card className="glass-dark border-white/10 h-[calc(100vh-8.5rem)] flex flex-col justify-between overflow-hidden relative">
       {/* ─── 1. FIXED HEADER (shrink-0) ─── */}
@@ -163,7 +160,7 @@ export function StepBilling({
                         <Calendar className="w-3.5 h-3.5 text-primary shrink-0 mt-0.5" />
                         <div className="space-y-0.5 flex-1">
                           <Label htmlFor="last-license-date" className="text-white text-[11px] font-bold block">
-                            Datum letzter CASPOS-Kauf (Stichtag)
+                            Datum letzter CASPOS-Kauf <span className="text-slate-400 font-normal">(optional)</span>
                           </Label>
                           <p className="text-[10px] text-slate-400 leading-tight">
                             Zur automatischen Berechnung der Update-Staffel (15% / 30% / 50%).
@@ -229,8 +226,7 @@ export function StepBilling({
         {/* Next Button */}
         <Button
           onClick={nextStep}
-          disabled={isNextDisabled}
-          className="w-full sm:w-auto bg-primary hover:bg-primary/90 text-white font-semibold px-5 shadow-md shadow-primary/20 h-8 text-xs gap-1.5 disabled:opacity-50"
+          className="w-full sm:w-auto bg-primary hover:bg-primary/90 text-white font-semibold px-5 shadow-md shadow-primary/20 h-8 text-xs gap-1.5"
         >
           Weiter zu Schritt 3 <ChevronRight className="w-3.5 h-3.5" />
         </Button>