fix: hide register tip on login and redirect to setup when no super admin (#3556)

## Changes
- Removed the "Register here" link from the login page — it misled users into thinking public registration was open.
- Added redirect from /login to /register when no super admin exists (initial setup).
- Added an info alert on the register page clarifying the page is only for initial setup; additional users are invited from team settings. Hidden for the invite-token flow.
- Extracted shared useSuperAdminRedirect hook to dedupe identical fetch/redirect logic across Login and Register.

## Benefits
- Clearer UX: login page no longer suggests self-registration is available post-setup.
- Correct routing on fresh installs: users land on the registration page instead of a login page they can't use.

client/src/Hooks/useSuperAdminRedirect.ts

@@ -0,0 +1,24 @@
+import { useEffect } from "react";
+import { useNavigate } from "react-router-dom";
+import { useGet } from "@/Hooks/UseApi";
+
+type Options = {
+	redirectTo: string;
+	redirectWhen: boolean;
+	skip?: boolean;
+};
+
+export const useSuperAdminRedirect = ({ redirectTo, redirectWhen, skip }: Options) => {
+	const navigate = useNavigate();
+	const { data: superAdminExists, isLoading } = useGet<boolean>(
+		skip ? null : "/auth/users/superadmin"
+	);
+
+	useEffect(() => {
+		if (!skip && superAdminExists === redirectWhen) {
+			navigate(redirectTo, { replace: true });
+		}
+	}, [superAdminExists, redirectWhen, redirectTo, skip, navigate]);
+
+	return { superAdminExists, isLoading };
+};

client/src/Pages/Auth/Login/index.tsx

@@ -10,6 +10,7 @@ import { useDispatch } from "react-redux";
 import { useNavigate } from "react-router-dom";
 import { setAuthState } from "@/Features/Auth/authSlice";
 import { usePost } from "@/Hooks/UseApi";
+import { useSuperAdminRedirect } from "@/Hooks/useSuperAdminRedirect";
 
 const LoginPage = () => {
 	const { t } = useTranslation();
@@ -17,6 +18,11 @@ const LoginPage = () => {
 	const navigate = useNavigate();
 	const { post, loading } = usePost();
 
+	const { isLoading: isCheckingAdmin } = useSuperAdminRedirect({
+		redirectTo: "/register",
+		redirectWhen: false,
+	});
+
 	const { schema, defaults } = useLoginForm();
 
 	const { control, handleSubmit } = useForm<LoginFormData>({
@@ -24,6 +30,8 @@ const LoginPage = () => {
 		defaultValues: defaults,
 	});
 
+	if (isCheckingAdmin) return null;
+
 	const onSubmit = async (data: LoginFormData) => {
 		if (loading) return;
 
@@ -82,12 +90,6 @@ const LoginPage = () => {
 				linkText={t("pages.auth.login.links.forgotPassword.linkText")}
 				href="/forgot-password"
 			/>
-			<TextLink
-				alignSelf={"center"}
-				text={t("pages.auth.login.links.register.text")}
-				linkText={t("pages.auth.login.links.register.linkText")}
-				href="/register"
-			/>
 		</BaseAuthPage>
 	);
 };

client/src/Pages/Auth/Register/index.tsx

@@ -1,11 +1,13 @@
 import { BaseAuthPage } from "@/Components/design-elements";
 import { Button, TextField } from "@/Components/inputs";
+import { Alert } from "@mui/material";
 import { useForm, Controller } from "react-hook-form";
 import { zodResolver } from "@hookform/resolvers/zod/dist/zod.js";
 import { useRegisterForm } from "@/Hooks/useRegisterForm";
 import type { RegisterFormData } from "@/Validation/register";
 import { useTranslation } from "react-i18next";
-import { usePost, useGet } from "@/Hooks/UseApi";
+import { usePost } from "@/Hooks/UseApi";
+import { useSuperAdminRedirect } from "@/Hooks/useSuperAdminRedirect";
 import { setAuthState } from "@/Features/Auth/authSlice";
 import { useDispatch } from "react-redux";
 import { useNavigate, useParams } from "react-router-dom";
@@ -32,21 +34,17 @@ const RegisterPage = () => {
 	const { post: verifyToken } = usePost<{ token: string }, InviteVerifyResponse>();
 	const hasVerified = useRef(false);
 
-	const { data: superAdminExists, isLoading: isCheckingAdmin } = useGet<boolean>(
-		token ? null : "/auth/users/superadmin"
-	);
+	const { isLoading: isCheckingAdmin } = useSuperAdminRedirect({
+		redirectTo: "/login",
+		redirectWhen: true,
+		skip: !!token,
+	});
 
 	const { control, handleSubmit, setError, reset } = useForm<RegisterFormData>({
 		resolver: zodResolver(schema),
 		defaultValues: defaults,
 	});
 
-	useEffect(() => {
-		if (superAdminExists === true) {
-			navigate("/login", { replace: true });
-		}
-	}, [superAdminExists, navigate]);
-
 	useEffect(() => {
 		if (!token || hasVerified.current) return;
 		hasVerified.current = true;
@@ -92,6 +90,9 @@ const RegisterPage = () => {
 			title={t("pages.auth.register.title")}
 			subtitle={t("pages.auth.register.subtitle")}
 		>
+			{!token && (
+				<Alert severity="info">{t("pages.auth.register.setupNotice")}</Alert>
+			)}
 			<Controller
 				name="firstName"
 				control={control}

client/src/locales/en.json

@@ -343,6 +343,7 @@
 			"register": {
 				"title": "Welcome back to Checkmate!",
 				"subtitle": "Sign up to get started",
+				"setupNotice": "This page is only available during initial setup. Once a super admin is registered, additional users can be invited from team settings.",
 				"submit": "Register"
 			},
 			"forgotPassword": {