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

CLAUDE.md

@@ -212,7 +212,8 @@ supplies:
   located and group posts go through `/clientapi/post/insert`), `AccountService` (profiles, relationships, follow,
   block, mute, follow requests, `/api/v2/search`, whose handles and URLs PrivaPub resolves), `ListService` (the
   persona's lists and their members; members are only accounts it follows, found with `accounts/search?following=true`),
-  `FilterService` (the persona's v2 filters, their keywords and filtered posts), `MediaService` (uploads), `GroupService`, `InstanceService` and `ProvenanceService`.
+  `FilterService` (the persona's v2 filters, their keywords and filtered posts), `DiscoveryService` (hashtags and
+  following them, trends, the directory), `MediaService` (uploads), `GroupService`, `InstanceService` and `ProvenanceService`.
 - **Reactions and votes are public** (owner decision, PrivaPub's ROADMAP): before a persona's first reaction or poll
   vote, `PublicNoticeService` asks it once (`PublicNoticeHost` in `MainLayout`) and remembers the persona in
   localStorage (`PublicActionNotices`). Anything else that makes a persona's act visible to others gets the same notice.
@@ -227,6 +228,10 @@ supplies:
   lists, notifications, public feeds, threads around the opened post, profiles; none for favourites, bookmarks,
   conversations and search), and the card leaves the post out (hide), folds it behind the filter's title (warn) or blurs
   its media (blur).
+- **Scheduled posts** (`Pages/Scheduled.razor` at `/scheduled`): the composer's clock button gives a Mastodon API post a
+  time (`scheduled_at`, at least five minutes ahead; located and group posts have none); the page moves or drops them.
+- **Explore** (`Pages/Explore.razor` at `/explore`): trending hashtags, posts and links (PrivaPub's, from public posts
+  it holds), the directory, and the hashtags the persona follows. A hashtag's feed tab follows it too.
 - **Mastodon DTOs** are client-side, in `Models/Mastodon/` (snake_case). `/clientapi` DTOs come from
   `PrivaPub.ClientModels`.
 - **Where a post is** (`InstanceService.Locate`, `Models/FeedPost.cs`): its own place (Pixelfed's, `privapub.place`),