Follow requests nobody answers are sent again

A Follow was resent only when the persona followed again. Lemmy 1.0
sends nothing it queued for a server before it started sending there, so
the Accept of a community follow made on first contact was lost for good:
the village's persona stayed "requested" a day while Lemmy listed her as a
follower, and every post the community announced was refused as not
followed. A request still unanswered is now sent again, the same activity,
after 15 minutes, an hour, 6 hours, a day, two and four days
(FollowResender, every 15 minutes); a server that holds the follow answers
the copy.

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

FEDERATION.md

@@ -224,6 +224,9 @@ Posts with a location (shown to nearby users of this server) never leave the ser
 - **Origins.** An actor document is accepted only from the address it names as its `id`. A key only if its actor lists
   it with `owner` set to the actor and on the actor's origin. An activity's `id`, and any object it creates, updates or
   deletes, must be on its actor's origin. An embedded object from another origin is fetched from that origin.
+- **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.
 - **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,