Bug: Navigation race condition in SignInPartner causing unintended redirects on unmount

# Bug report <!-- ⚠️ We receive a lot of bug reports which have already been solved or discussed. If you are looking for help, please try these first: - Docs: https://docs.supabase.com - Discussions: https://github.com/supabase/supabase/discussions - Discord: https://discord.supabase.com Before opening a bug report, please verify the following: --> - [X] I confirm this is a bug with Supabase, not with my own application. - [X] I confirm I have searched the [Docs](https://docs.supabase.com), GitHub [Discussions](https://github.com/supabase/supabase/discussions), and [Discord](https://discord.supabase.com). ## Describe the bug There is a navigation race condition in `apps/studio/components/interfaces/SignIn/SignInPartner.tsx` caused by an unguarded asynchronous operation inside a `useEffect`. On mount, an IIFE is triggered to fetch `auth.getSession()` and potentially `auth.signInWithIdToken()`. If the user navigates away from this page (unmounting the component) before these network promises resolve, the `finally` or `else` blocks will still blindly execute `router.replace()`. This creates a ghost redirect that hijacks the user's session and yanks them away from whatever new page they navigated to. ## To Reproduce Steps to reproduce the behavior: 1. Open your browser's network tab and throttle the speed to "Slow 3G" (to easily catch the race condition). 2. Navigate to the partner sign-in route with mock parameters (e.g., `/sign-in-partner?partner=foo&id_token=bar`). 3. While the `Loader2` is spinning, immediately click the browser's "Back" button or click a link to navigate away to a different dashboard page. 4. Wait a few seconds for the pending authentication promises to resolve in the background. 5. See error: You are forcefully redirected to `/sign-in-mfa` or `/sign-in`, overriding your explicit navigation. ## Expected behavior The `useEffect` should respect the component lifecycle. If the component unmounts before the authentication promises resolve, the rout…