A follow request sent again carries a new id

Lemmy keeps the ids of the activities it received and never answers one again, so resending the same Follow could not
heal a follow whose Accept it lost: the village's community follow stayed pending through two resends. Each resend is
now the same follow under its own id (<follow id>-again-<n>), and an Accept naming any of them answers the follow;
the Undo still embeds the follow, so servers match it by its actor and object. Sent this way, the stuck follow was
accepted at once.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

FEDERATION.md

@@ -230,9 +230,10 @@ Posts with a location (shown to nearby users of this server) never leave the ser
   is read again from its author's server, a deletion of a public or unlisted post is applied once that server answers
   404 or 410, and anything else is dropped. LD signatures are not verified. A reply forwarded this way is kept when
   someone here follows the author of the post it answers, as Mastodon does.
-- **Follow requests** still unanswered are sent again after 15 minutes, an hour, 6 hours, a day, two and four days, the
-  same activity each time: a server can take a Follow and lose its answer (Lemmy 1.0 sends nothing it queued for a
-  server before it started sending there), and one that holds the follow already answers the copy.
+- **Follow requests** still unanswered are sent again after 15 minutes, an hour, 6 hours, a day, two and four days: a
+  server can take a Follow and lose its answer (Lemmy 1.0 sends nothing it queued for a server before it started
+  sending there), and one that holds the follow answers it again. Each is the same follow under a new id
+  (`…/follow-<id>-again-<n>`), since Lemmy ignores an id it has seen; an answer naming any of them counts.
 - **Fetching.** All fetches are signed by the instance actor. They go only to public addresses, follow at most three
   redirects and read at most 1 MB.
 - **Threads.** A reply's missing parents are fetched, up to 10 levels. When someone here opens a public remote thread,