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

PrivaPub/Models/Post/Post.cs

@@ -57,6 +57,13 @@ namespace PrivaPub.Models.Post
 		public string Url { get; set; }
 		public string ContextURI { get; set; }
 		public string QuoteURI { get; set; }
+		public string QuotedPostId { get; set; }//our copy of the quoted post, once fetched
+		public QuoteState QuoteState { get; set; }
+		public string QuoteAuthorizationURI { get; set; }//FEP-044f: the quoted author's stamp
+		public bool QuoteByConsent { get; set; }//our quote of a post whose server asks for consent (FEP-044f), so `quote` is sent
+		public int QuotesCount { get; set; }
+		[BsonIgnoreIfNull]
+		public InteractionRule QuotePolicy { get; set; }//a remote post's interactionPolicy.canQuote; null when it states none
 		public List<string> To { get; set; } = new();
 		public List<string> Cc { get; set; } = new();
 
@@ -73,6 +80,17 @@ namespace PrivaPub.Models.Post
 		public string UpdateReason { get; set; }
 	}
 
+	public enum QuoteState
+	{
+		None,
+		Pending,
+		Accepted,
+		Rejected,
+		Revoked,
+		Deleted,
+		Unauthorized
+	}
+
 	public enum PostVisibility
 	{
 		Public,