fix: add ApiError type cast in pj-registration onError handler

The onError callback in useMutation provides Error type, but
handleError expects ApiError. Added 'as ApiError' cast and imported
the ApiError type from @/client to fix the TypeScript build error.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: Romularques

frontend/src/routes/pj-registration.tsx

@@ -6,6 +6,7 @@ import { useForm } from "react-hook-form"
 import { z } from "zod"
 
 import {
+  type ApiError,
   type CompanyPublic,
   type CompanyRegistrationComplete,
   InvitesService,
@@ -427,7 +428,7 @@ function PjRegistration() {
     },
     onError: (err) => {
       setConfirmOpen(false)
-      handleError.call(showErrorToast, err)
+      handleError.call(showErrorToast, err as ApiError)
     },
   })