415200d8f0
Adds a stable client_id column to auth_session for the upcoming PlayEventsReporter. Lazily generated on first read by the reporter; deliberately survives sign-out since it's a device install identity, not a session value. DB version bump 3→4 (destructive migration per the pre-release policy). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>