P6 done: personas can be quoted, under the owner's default of anyone, automatically

- Our public and unlisted posts state interactionPolicy.canQuote. The policy comes from the post, then the persona
  (`source[quote_policy]`: public, followers or nobody; default public as the owner chose), and is always nobody for
  followers-only posts and DMs.
- QuoteRequests are answered with Accept{result} naming a parrot-licence at /peasants/{name}/parrot-licences/{id}
  (the route name the owner chose), or with Reject. Followers-only checks that the requester really follows.
- A licence is a QuoteAuthorization naming both posts; revoking it (POST /api/v1/statuses/:id/quotes/:quoting_id/revoke)
  marks it 410, sends Delete{licence} to the quoter and the persona's followers, and revokes our own copy of the quote.
- A quote that arrives with one of our licences is accepted only if that licence is ours, unrevoked and names exactly
  that quoting post. One persona quoting another gets a licence too.
- Mastodon API: quote_approval for our posts (automatic, followers, current_user), `quote_approval_policy` when posting,
  PUT /api/v1/statuses/:id/interaction_policy, `source.quote_policy`.

Checked live: GoToSocial still accepts our posts with the policy stated, and leaves likes, replies and boosts open.

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

PrivaPub.Tests/Support/Harness.cs

@@ -58,6 +58,7 @@ namespace PrivaPub.Tests.Support
 				new UndoHandler(Db, Local, Reactions),
 				new LikeHandler(Db, Reactions),
 				new EmojiReactHandler(Db, Reactions),
+				new QuoteRequestHandler(Quotes),
 				new DislikeHandler(Db),
 				new JoinHandler(Db, Local, Delivery),
 				new AnnounceHandler(Db, Local, RemotePosts, Fanout, Remote),