P6: quote posts, received and sent (FEP-044f and the older keys)

- Received quotes: read from `quote`, `quoteUrl`, `quoteUri`, `_misskey_quote` or a FEP-e232 Link tag; the quoted post
  is fetched once; a quoteAuthorization stamp is verified field by field on the quoted author's origin; a consent
  quote without a stamp is pending; an older-key quote of a public post is shown; Delete of a stamp revokes. Counts
  and a `quote` notification follow the accepted state. The `quote-inline` fallback survives sanitising and is removed
  from content when the real quote is shown.
- Personas quote through `quoted_status_id`: posts that state a quote policy get a QuoteRequest and stay pending until
  an Accept brings a stamp we can verify, then an Update adds quoteAuthorization; posts that state none are quoted
  the older way, without `quote`; another persona's posts cannot be quoted yet (we issue no stamps). Quoting posts
  are delivered to the quoted author too.
- Mastodon API: Status.quote (with the quoted status one level deep), quotes_count, quote_approval from the remote
  policy, GET /api/v1/statuses/:id/quotes, `quote` notifications, and api_versions.mastodon = 7.

Checked live: GoToSocial's author-only quote policy is respected.

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

docs/ROADMAP.md

@@ -453,9 +453,11 @@ it, raw where it doesn't.
 - **Polls** in and out, with the Misskey, Pleroma and PieFed vote shapes. A count refresh is never an edit (done in
   v1.10.0; checked live both ways against GoToSocial).
 - **Quotes (FEP-044f):**
-  - 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).
+  - read every key; verify `QuoteAuthorization` on all of its fields; handle revocation (done in v1.13.0);
+  - personas quote others: `quoted_status_id`, `QuoteRequest`, `Accept{result}` verified, `Update` with
+    `quoteAuthorization`; legacy quotes for posts that state no policy (done in v1.13.0); `api_versions.mastodon = 7`;
+  - still open: be quotable (`canQuote` on our posts, answer `QuoteRequest`, serve and revoke stamps). It needs a themed
+    route name for stamps, agreed with the owner, and a default quote policy.
 - **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** (done in v1.12.0):