fix(frontend): Add missing RefreshCw import to PlatformSettings

The Tiers & Pricing tab was crashing with "RefreshCw is not defined"
because the icon was used but not imported from lucide-react.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/pages/platform/PlatformSettings.tsx

@@ -25,6 +25,7 @@ import {
   Users,
   ExternalLink,
   Mail,
+  RefreshCw,
 } from 'lucide-react';
 import {
   usePlatformSettings,