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/Api/Mastodon/Controllers/PollsController.cs

@@ -0,0 +1,54 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+using PrivaPub.Api.Mastodon.Infrastructure;
+using PrivaPub.Api.Mastodon.Mappers;
+using PrivaPub.Domain.Privacy;
+using PrivaPub.Domain.Statuses;
+using PrivaPub.Models.Post;
+using PrivaPub.StaticServices;
+
+using PostEntity = PrivaPub.Models.Post.Post;
+
+namespace PrivaPub.Api.Mastodon.Controllers
+{
+	public class PollsController : MastodonController
+	{
+		readonly DbEntities _dbEntities;
+		readonly MastodonMapper _mapper;
+		readonly IPollService _polls;
+
+		public PollsController(DbEntities dbEntities, MastodonMapper mapper, IPollService polls)
+		{
+			_dbEntities = dbEntities;
+			_mapper = mapper;
+			_polls = polls;
+		}
+
+		[HttpGet("/api/v1/polls/{id}"), Scope("read:statuses", requiresUser: false), AllowAnonymous]
+		public async Task<IActionResult> Get(string id, CancellationToken token)
+		{
+			var post = await Visible(id, token);
+			return post?.Poll == default ? NotFoundError() : Json(_mapper.Poll(post, MyId, await _polls.OwnVotes(post.ID, MyId, token)));
+		}
+
+		[HttpPost("/api/v1/polls/{id}/votes"), Scope("write:statuses")]
+		public async Task<IActionResult> Vote(string id, CancellationToken token)
+		{
+			var post = await Visible(id, token);
+			if (post?.Poll == default)
+				return NotFoundError();
+			var choices = Params.List("choices").Select(c => int.TryParse(c, out var index) ? index : -1).ToList();
+			var outcome = await _polls.Vote(Me, post, choices, token);
+			if (!outcome.Ok)
+				return Error(outcome.Status, outcome.Error);
+			return Json(_mapper.Poll(outcome.Post, MyId, await _polls.OwnVotes(post.ID, MyId, token)));
+		}
+
+		async Task<PostEntity> Visible(string id, CancellationToken token)
+		{
+			var post = await _dbEntities.Posts.Match(p => p.ID == id && !p.DeletedAt.HasValue).ExecuteFirstAsync(token);
+			return post != default && post.Visibility != PostVisibility.LocalGeo && await VisibilityPolicy.CanSee(post, MyId, token) ? post : default;
+		}
+	}
+}