feat: quick polls in comments that end in a decision

«📊 Añadir una encuesta» adds 2 to 6 options to a new comment. Members,
viewers too, vote by clicking an option (one vote each, which they can
change or take back) and see each option's votes as a bar. Whoever
started it, or an admin, closes it with «Cerrar y decidir»: the most
voted wins (none on a tie) and a «Decidido: …» reply marked as a
decision shows above the ticket. Events of the comment (voted, closed).

API: addComment(…, poll), votePoll, closePoll, Comment.poll;
POST /api/comments/{id}/poll/vote and …/poll/close. MCP: add_comment
poll, vote_poll, close_poll.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

libs/api/tracker/application/src/lib/commands/add-comment.command.ts

@@ -8,6 +8,8 @@ export class AddCommentCommand extends Command<CommandResult> {
     public readonly body: string,
     /** Comment it answers; a reply to a reply joins the same thread. */
     public readonly replyTo: string | null = null,
+    /** A quick poll's options (2–6), if any. */
+    public readonly poll: string[] | null = null,
   ) {
     super();
   }