feat: redirect authenticated users from signup page (#23766)

* feat: redirect authenticated users from signup page

- Add session check in signup getServerSideProps
- Redirect to redirect parameter if present, otherwise to root
- Follows existing authentication patterns in codebase

Co-Authored-By: peer@cal.com <peer@cal.com>

* fix test

* fix test

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: unknown <adhabal2002@gmail.com>
Co-authored-by: Anik Dhabal Babu <81948346+anikdhabal@users.noreply.github.com>

apps/web/lib/signup/getServerSideProps.tsx

@@ -1,6 +1,7 @@
 import type { GetServerSidePropsContext } from "next";
 import { z } from "zod";
 
+import { getServerSession } from "@calcom/features/auth/lib/getServerSession";
 import { getOrgUsernameFromEmail } from "@calcom/features/auth/signup/utils/getOrgUsernameFromEmail";
 import { checkPremiumUsername } from "@calcom/features/ee/common/lib/checkPremiumUsername";
 import { isSAMLLoginEnabled } from "@calcom/features/ee/sso/lib/saml";
@@ -42,6 +43,19 @@ export const getServerSideProps = async (ctx: GetServerSidePropsContext) => {
 
   const redirectUrl = redirectUrlData.success && redirectUrlData.data ? redirectUrlData.data : null;
 
+  const session = await getServerSession({
+    req: ctx.req,
+  });
+
+  if (session?.user?.id) {
+    return {
+      redirect: {
+        permanent: false,
+        destination: redirectUrl || "/",
+      },
+    } as const;
+  }
+
   const props = {
     redirectUrl,
     isGoogleLoginEnabled: IS_GOOGLE_LOGIN_ENABLED,

apps/web/playwright/organization/organization-invitation.e2e.ts

@@ -304,6 +304,9 @@ test.describe("Organization", () => {
       });
 
       await test.step("Signing up with the previous username of the migrated user - shouldn't be allowed", async () => {
+        await orgOwner.logout();
+        await page.goto("/");
+        await page.waitForLoadState();
         await page.goto("/signup");
         await expect(page.locator("text=Create your account")).toBeVisible();
         await expect(page.locator('[data-testid="continue-with-email-button"]')).toBeVisible();