Posts for later, hashtags followed, and Explore

The composer's clock button gives a post a time (scheduled_at, at least five
minutes ahead; located and group posts have none), and /scheduled moves or
drops what waits. A hashtag's feed tab shows its week and follows it, so its
public posts come home. Explore (/explore) shows what PrivaPub says is
trending, hashtags, posts and links from public posts it holds, the
directory by activity or by joining, and the hashtags the persona follows.
DiscoveryService does the calls; the e2e tests check each against PrivaPub's
own answer.

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

MastodonJsonContext.cs

@@ -42,6 +42,12 @@ namespace decePubClient;
 [JsonSerializable(typeof(List<Filter>))]
 [JsonSerializable(typeof(FilterForm))]
 [JsonSerializable(typeof(FilterStatus))]
+[JsonSerializable(typeof(ScheduledStatus))]
+[JsonSerializable(typeof(List<ScheduledStatus>))]
+[JsonSerializable(typeof(ScheduleForm))]
+[JsonSerializable(typeof(Tag))]
+[JsonSerializable(typeof(List<Tag>))]
+[JsonSerializable(typeof(List<TrendLink>))]
 public partial class MastodonJsonContext : JsonSerializerContext
 {
 }