fix(ap): self-heal v6 - retroactively restore covers on cached boosts
The resolveRemoteNote image-fallback (1.3.3) only helps NEW boosts:
upsertBoostedNote uses INSERT OR IGNORE, so a boost cached coverless
before the fix keeps its empty media_json forever, even on re-boost.
Bump SELFHEAL_VERSION 5 -> 6 so every instance re-fetches its cached
timeline notes once at boot; mediaFromNote (which has the image
fallback) refreshes the media and the cover appears.
Verified against the real note: the reported post (Swimming Pools,
android.sound-fabrics.com) carries its cover in note.image with no
attachment - exactly what the heal re-reads.
Co-Authored-By: Claude <noreply@…>