feat: add resend capability for platform and account invite codes

Revoke-and-recreate flow for both invite systems with email delivery
via Resend API. Includes account invite email template and audit logging.

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

frontend/src/api/admin.ts

@@ -56,6 +56,8 @@ export const adminApi = {
     api.post<InviteCodeResponse>('/invites', data).then(r => r.data),
   deleteInviteCode: (code: string) =>
     api.delete(`/invites/${code}`),
+  resendInviteCode: (code: string) =>
+    api.post<InviteCodeResponse>(`/invites/${code}/resend`).then(r => r.data),
 
   // Audit Logs
   listAuditLogs: (params?: Record<string, unknown>) =>