fix(billing): don't re-throw server action error in manual transfer form

The catch block showed a toast but then re-threw the error, causing Next.js
to attempt a Server Component re-render that crashed with a generic 500 error.
Now the error is handled by the toast and swallowed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: guillermoscript

app/[locale]/dashboard/admin/billing/upgrade/upgrade-page-client.tsx

@@ -78,7 +78,6 @@ export function UpgradePageClient({ plans, currentPlan }: UpgradePageClientProps
       setManualSubmitted(true)
     } catch (e: any) {
       toast.error(e.message || t('submitError'))
-      throw e
     }
   }