Velog single-post archiving (fixes #24)
Velog post URLs (velog.io/@user/<slug>) are now archivable — the modal recognizes them and the Archive button enables. Existing Velog profile subscriptions (velog.io/@user) are unchanged.
Medium and Brunch share the same /@user/<id> shape and got safer internal post-ID handling at the same time. No user-facing change.
Billing notifications in Settings (new)
Active billing events (trial expiring, payment issue, plan changes, etc.) now surface in Settings → Social Archiver. High-severity events also fire a one-time Notice. Anything payment-related routes you to the mobile app, per Obsidian plugin policy.
Mirrors what the mobile app has shown since 3.5.0.