Fixed ActivityPub follower fanout for published posts. The earlier Mastodon follow fix handled Accept delivery, but post delivery to followers still used Fedify's default #main-key sender path. Slugkit now signs follower fanout with the Fedify 2 multikey id Mastodon expects, so new posts appear on the Mastodon profile after publishing.

Fixed the Mastodon follow flow for @slug@slugkit.com. The site now signs outbound ActivityPub Accept delivery with the Fedify 2 multikey id Mastodon expects, so follow requests no longer remain stuck as pending.