[Auth] Login breaks when already logged in

### Environment

SaaS ([https://sentry.io/]())

### Steps to Reproduce

1. login to Sentry org A with user X
2. go to the login page for Sentry org B and attempt to login with user Y
3. be redirected to Sentry org A subdomain when entering Authenticator Code
4. get redirected to Sentry org A login page without a valid session

### Expected Result

User X session is invalidated and User Y session starts.

### Actual Result

This flow is not possible. In order to switch between users seamlessly Sentry users must maintain separate browser contexts which is very cumbersome.

### Product Area

Sign In

### Link

[https://sentry.zendesk.com/agent/tickets/127996]()

### DSN

*No response*

### Version

SAAS

We want to define a set of [lightweight metrics]() that SDKs can automatically collect for e.g. framework, language or platform, focusing only on signals that **do NOT overlap with Tracing**. Ideally these metrics should give a quick sense of app or runtime health, … while deeper investigation will still rely on traces or profiles.

Examples**:**

* Node.js runtime metrics (e.g., event loop delay, heap usage)
* Prisma-related metrics in Next.js
* Mobile CPU / memory usage to help surface potential ANRs or app hangs

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**Candidate Metrics (add more below)**

* …

*(please also add ideas, questions or examples in comments)*