fix: accept price in currency units instead of cents in product form

Il campo prezzo del form admin ora accetta valori in unità (es. 19.99)
invece di centesimi (1999). La conversione *100 avviene al submit,
il DB e Stripe continuano a ricevere centesimi.

app/src/app/admin/products/[id]/page.tsx

@@ -82,7 +82,7 @@ export default function AdminProductEditPage() {
               title: p.title,
               slug: p.slug,
               description: p.description,
-              basePrice: String(p.basePrice),
+              basePrice: (p.basePrice / 100).toFixed(2),
               currency: p.currency,
               status: p.status,
               attributes: JSON.stringify(p.attributes, null, 2),
@@ -171,7 +171,7 @@ export default function AdminProductEditPage() {
       title: form.title,
       slug: form.slug,
       description: form.description,
-      basePrice: parseInt(form.basePrice),
+      basePrice: Math.round(parseFloat(form.basePrice) * 100),
       currency: form.currency,
       status: form.status,
       attributes,
@@ -262,11 +262,12 @@ export default function AdminProductEditPage() {
 
           <div className="grid grid-cols-2 gap-4">
             <Input
-              label="Base Price (cents)"
+              label={`Base Price (${form.currency})`}
               type="number"
               value={form.basePrice}
               onChange={(e) => setForm((f) => ({ ...f, basePrice: e.target.value }))}
               min="0"
+              step="0.01"
               required
             />
             <Select