Introduces a UserSeriesFollow model with a dedicated join table so users
can follow/unfollow series and receive socket notifications when new
books are added to followed series. The user JSON response now includes a
seriesFollowing array, and three new API endpoints are available under
/api/me/follows/.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
