Phase 5: Translate Auth Pages - login and signup

- Create auth.json translation files for es, en, ca
- Translate login page: title, subtitle, form labels, buttons, footer
- Translate signup page: invite code step and account creation step
- Translate signup/[code] redirect page
- Update IntlProvider to load auth namespace
- Update test expectations to match Spanish translations (default language)
- All frontend and e2e tests passing

frontend/app/signup/[code]/page.tsx

@@ -4,12 +4,14 @@ import { useEffect } from "react";
 import { useRouter, useParams } from "next/navigation";
 import { useAuth } from "../../auth-context";
 import { LanguageSelector } from "../../components/LanguageSelector";
+import { useTranslation } from "../../hooks/useTranslation";
 
 export default function SignupWithCodePage() {
   const params = useParams();
   const router = useRouter();
   const { user, isLoading } = useAuth();
   const code = params.code as string;
+  const t = useTranslation("auth");
 
   useEffect(() => {
     // Wait for auth check to complete before redirecting
@@ -40,7 +42,7 @@ export default function SignupWithCodePage() {
       <div style={{ position: "absolute", top: "1rem", right: "1rem" }}>
         <LanguageSelector />
       </div>
-      Redirecting...
+      {t("signup.redirecting")}
     </main>
   );
 }