feat(fediverse): self-heal the timeline cache once per SELFHEAL_VERSION bump
selfHealTimeline() re-fetches cached ap_timeline notes and refreshes content +
media (recovers covers/edits delivered during a flux window, e.g. a fleet-wide
update) and drops gone (404/410) notes. Gated by a selfheal_version setting so it
runs ONCE after a SELFHEAL_VERSION bump, not on every boot. Async + bounded
(latest 200) like autoMigrateCircles. Closes prutfolio-src-5gl.
Co-Authored-By: Claude <noreply@…>