[Bug]: Prevent users getting stuck in welcome flow after setup on another device

[voyager-slama]

Describe the bug

A user can get trapped in the welcome flow despite the app already being configured on a different device. Detect existing setup state and provide a reliable recovery path.

How can we recreate this bug?

1. Follow the affected workflow described above.
2. Observe the behavior.

Expected behavior

Multi-device access should not re-run or trap users in setup.

MatchExec Version

Unknown — migrated from Todoist; determine during triage.

Docker Version

Unknown — migrated from Todoist; determine during triage.

Additional context

Multi-device access should not re-run or trap users in setup.

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Migrated from Todoist by voyager[bot].