An event card joins and leaves the event

PrivaPub lets a persona join another server's event (owner decision
2026-10-05). The card of a remote event shows the persona's participation
(pending, accepted, rejected) with Join or Leave, except for events by
invitation or taken on another site. Joining is public on the event's
server, so the first join asks the persona once, as reactions and votes do,
remembered apart from them (PublicAct).

The e2e joins the event SocialPub's Mobilizon scenario keeps, checks the
participant on Mobilizon and PrivaPub's answer, and leaves it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

Models/Mastodon/PrivaPubStatus.cs

@@ -73,9 +73,13 @@ public class PrivaPubEvent
 	public string TimeZone { get; set; }
 	public List<PrivaPubPlace> Places { get; set; } = [];
 	public string OnlineUrl { get; set; }
+	/// <summary>Mobilizon's: "free", "restricted" (the organiser approves), "invite" or "external" (not joined from here).</summary>
+	public string JoinMode { get; set; }
 	public int? Participants { get; set; }
 	public int? Capacity { get; set; }
 	public string Status { get; set; }
+	/// <summary>The persona's own: "pending", "accepted" or "rejected"; null when it has not joined.</summary>
+	public string Participation { get; set; }
 }
 
 public class PrivaPubPlace