P6: custom emoji, fuller remote profiles, and polls both ways

- Custom emoji (Emoji tags) on posts, display names, bios and profile fields, at most 64 per object, proxied, in
  Status.emojis and Account.emojis.
- Remote profiles keep their header, profile fields, locked flag, published date, movedTo, indexable, memorial and
  image descriptions (a locked GoToSocial account no longer shows as open).
- Polls: incoming Questions (Mastodon, Misskey, Pleroma, GoToSocial shapes) with counts, voters, end and closed;
  our own polls from the Mastodon API go out as Questions; votes in are counted once per voter and never become
  replies; personas vote on other servers' polls with one Note per choice; counts refresh with an Update at most every
  three minutes; a poll closes on time and tells its voters and its author. GET /api/v1/polls/:id and POST
  /api/v1/polls/:id/votes.
- An Update without a newer `updated` only refreshes poll, video, audio and event details and leaves no revision.

Checked live against GoToSocial: each side's poll reaches the other as a poll and each side's vote is counted.

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

PrivaPub.Tests/Federation/ActorProfileTests.cs

@@ -0,0 +1,41 @@
+using PrivaPub.Federation.Actors;
+
+using System.Text.Json;
+
+namespace PrivaPub.Tests.Federation
+{
+	public class ActorProfileTests
+	{
+		[Fact]
+		public void Reads_a_mastodon_profile_with_its_header_fields_emoji_and_lock()
+		{
+			using var json = JsonDocument.Parse("""
+				{
+					"id": "https://m.example/users/ann", "type": "Person", "preferredUsername": "ann", "name": "Ann :sparkle:",
+					"inbox": "https://m.example/users/ann/inbox", "manuallyApprovesFollowers": true, "indexable": true, "memorial": false,
+					"published": "2023-04-01T00:00:00Z", "movedTo": "https://n.example/users/ann",
+					"icon": { "type": "Image", "url": "https://m.example/a.png", "summary": "a cat" },
+					"image": { "type": "Image", "url": "https://m.example/h.png", "name": "mountains" },
+					"tag": [{ "type": "Emoji", "name": ":sparkle:", "icon": { "type": "Image", "url": "https://m.example/emoji/sparkle.png" } }],
+					"attachment": [
+						{ "type": "PropertyValue", "name": "Site", "value": "<a href=\"https://ann.example\" rel=\"me\">ann.example</a><script>x</script>" },
+						{ "type": "PropertyValue", "name": "Pronouns", "value": "she/her" }
+					]
+				}
+				""");
+
+			var actor = ActorDocument.Parse(json.RootElement);
+
+			Assert.True(actor.Locked);
+			Assert.True(actor.Indexable);
+			Assert.Equal("https://m.example/h.png", actor.Header);
+			Assert.Equal("a cat", actor.IconDescription);
+			Assert.Equal("mountains", actor.HeaderDescription);
+			Assert.Equal("https://n.example/users/ann", actor.MovedTo);
+			Assert.Equal(new DateTime(2023, 4, 1, 0, 0, 0, DateTimeKind.Utc), actor.Published);
+			Assert.Equal("sparkle", Assert.Single(actor.Emojis).Shortcode);
+			Assert.Equal(new[] { "Site", "Pronouns" }, actor.Fields.Keys);
+			Assert.DoesNotContain("<script>", actor.Fields["Site"]);
+		}
+	}
+}