P6: emoji reactions in and out

- Incoming reactions in all three shapes: Misskey and Sharkey Likes carrying an emoji (`content` or
  `_misskey_reaction`), Pleroma, Akkoma and Iceshrimp.NET EmojiReacts, and their Undo. Unicode reactions are one
  grapheme; custom ones need their Emoji tag and keep its image; `:name@host:` is read as `name`. A Like whose
  content is a heart stays a favourite.
- Reactions are kept per account and emoji on our posts and on remote ones we hold, and the author of a local post
  gets a `pleroma:emoji_reaction` notification with the emoji.
- Personas react through Pleroma's API (PUT/DELETE /api/v1/pleroma/statuses/:id/reactions/:emoji, GET for the list),
  which sends an EmojiReact (or its Undo) to the post's author.
- Statuses carry `emoji_reactions` (read by Phanpy) and `pleroma.emoji_reactions`, with counts and whether the viewer
  reacted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

docs/ROADMAP.md

@@ -456,7 +456,8 @@ it, raw where it doesn't.
   - read every key; verify `QuoteAuthorization` on all of its fields; handle revocation;
   - be quotable: `canQuote`, answer `QuoteRequest`, serve and revoke stamps;
   - then advertise `api_versions.mastodon ≥ 7` (4.5.0).
-- **Emoji reactions** in all three inbound forms, plus outbound `EmojiReact`, exposed as `emoji_reactions`.
+- **Emoji reactions** in all three inbound forms, plus outbound `EmojiReact`, exposed as `emoji_reactions` (done in
+  v1.11.0; Pleroma's `/api/v1/pleroma/statuses/:id/reactions` endpoints and `pleroma:emoji_reaction` notifications).
 - **Link cards:**
   - from the object, or from FEP-8967 `preview`, without fetching;
   - fetching the page itself is the owner's decision (INTEROP §6.1).