Sign-in hangs on the loading spinner in Android's "Add Google Workspace account"

### Describe the bug

When adding a Google Workspace account on Android (Settings → Add account → Google), Google opens the IdP sign-in in its embedded account-setup WebView (`com.google.android.gms.auth.uiflows.minutemaid.MinuteMaidActivity`; UA ends with `MinuteMaid`, engine SystemWebViewGoogle 149 — a current Chromium, so this is not an old-engine problem). authentik is the SAML IdP for the Workspace domain.

The user completes the full flow (identification → password → MFA). Server-side everything succeeds — the `login` event is created and the session is established — but the flow UI stays on the loading spinner forever. The expected follow-up request `GET /application/saml//?SAMLRequest=...` (the flow's `?next=`, which would produce the autosubmit POST back to Google's ACS) is never made. The same flow works fine in desktop and mobile browsers.

### How to reproduce

1. Google Workspace with SAML SSO via authentik (SP-initiated). Brand default authentication flow: identification → password → authenticator validation (webauthn and/or totp) → user_login.
2. On Android (tested: Android 16, Galaxy S24+, SystemWebViewGoogle 149.0.7827.164), add the Workspace account via Settings → Add account → Google.
3. Enter email and password, complete MFA (TOTP or passkey — same result).
4. Observe: server logs show the `login` event created; the WebView stays on the spinner; `/application/saml//` is never requested.

### Expected behavior

After the flow completes, the executor's redirect challenge navigates to `/application/saml//`, which autosubmits the SAMLResponse to Google's ACS and finishes the account setup. Cancelling WebAuthn should fall back to the device picker.

### Screenshots

_No response_

### Additional context

_No response_

### Deployment Method

Kubernetes

### Version

2026.5.3

### Relevant log output

```shell

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