T12, T13: Sharkey and Akkoma in the pasture, and two bugs Akkoma found

Sharkey 2025.4.7 is the Misskey peer under another name, image, database, Redis db and
home. Its scenario is Misskey's plus edits both ways and the FEP-e232 quote tag: 40 checks
pass.

Akkoma 3.20.1 publishes no image, so tools/pasture/images/akkoma installs its OTP
release, pinned by checksum, and appends Caddy's CA to the CA bundles the release ships.
Its scenario has 44 checks, which pass three runs in a row:
- follows, posts, CW, followers-only posts and the published time;
- replies, likes, boosts and their undos;
- EmojiReact both ways and withdrawn;
- DMs, polls, quotes, media, edits with history and deletes, both ways;
- unfollow, block, unblock and statistics.

The two bugs, both fixed:
- Followers-only posts arrived as DMs on Pleroma and Akkoma. They call a post private
  only if an address in `to` contains "/followers" or its cc is not empty. Ours is
  /groupies, and a post mentioning nobody had an empty cc. The followers collection is now
  named in cc as well, which tells nobody anything new.
- Akkoma's open polls showed as ended and refused votes. Akkoma carries an open poll's
  end in `closed` and sends no `endTime`. A `closed` in the future is now read as the end.

Neither of these is a PrivaPub bug:
- Akkoma's Linkify never takes @user@host.test for a mention, so its DM addresses alice
  with to[].
- Its API never reports a remote blocker as blocked_by, so the block is read from its
  database.

Also in this commit:
- The rate limits are configuration (RateLimits: AccountsPerMinute, InboxBurst,
  InboxPerTenSeconds), with the old values as defaults. The pasture raises the accounts
  limit, which back-to-back runs from one address had hit.
- A new Lemmy never sends what it queued for a server before it started that server's
  send worker, so the scenario waits for the worker before its first follow.

All six peers in one clean pass: GoToSocial 54 (+1 expected), Mastodon 49 (+2), Misskey
35, Sharkey 40, Akkoma 44, and Lemmy 20 (+3) once the worker wait was added. 642 tests
pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ELjqpznMFMNrJoJUj6K5p2

tools/pasture/Caddyfile

@@ -32,3 +32,8 @@ lemmy.test {
 	tls internal
 	reverse_proxy pasture-lemmy:8536
 }
+
+akkoma.test {
+	tls internal
+	reverse_proxy pasture-akkoma:4000
+}