fix: attach anchor to document before click for Firefox download compatibility

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/scripts/ScriptGeneratorPanel.tsx

@@ -44,7 +44,9 @@ export function ScriptGeneratorPanel() {
     const a = document.createElement('a')
     a.href = url
     a.download = `${selectedTemplate.slug}.ps1`
+    document.body.appendChild(a)
     a.click()
+    document.body.removeChild(a)
     URL.revokeObjectURL(url)
   }