R4 server pieces: typed admin statistics, DELETE media, accounts by ids, hashtag history in search

Completion program R4 (the client catching up), the server's part.

- /clientapi/admin/statistics/hosts/{host}, /events and /server answer typed views (ViewHostDetail, ViewHostInstance,
  ViewHostDay, ViewInteractionEvent, ViewServerDay in ClientModels) instead of an anonymous object and raw entities:
  the instance's public description, never its raw instance API document; the events without their actor hash. The
  JSON names stay, so lib/interop.sh's stats_check reads them as before.
- DELETE /api/v1/media/{id} (Mastodon 4.4): a persona's own upload goes to the trash while nothing holds it; a posted
  or scheduled one answers 422.
- GET /api/v1/accounts?id[]= (Mastodon 4.3): up to 40 accounts, those that exist.
- /api/v2/search's hashtags carry their week of use (TagsController.History), not an empty history.

Verified: dotnet build PrivaPub.sln -c Release; the pasture: gts 64/64 (statistics included); by hand, an unattached
upload deleted (then 404), a posted one refused (422), accounts by ids, a hashtag's history.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WpVCoDeM1qUTRp4fXQdfof

PrivaPub/Api/Mastodon/Controllers/MediaController.cs

@@ -64,6 +64,20 @@ namespace PrivaPub.Api.Mastodon.Controllers
 			};
 		}
 
+		// Mastodon 4.4: a persona's own upload, while nothing holds it (not posted, not scheduled, not a profile picture), goes to
+		// the trash as the janitor would take it
+		[HttpDelete("/api/v1/media/{id}"), Scope("write:media")]
+		public async Task<IActionResult> Delete(string id, CancellationToken token)
+		{
+			var attachment = await DB.Default.Find<MediaAttachment>().Match(m => m.ID == id && m.OwnerAvatarId == MyId && m.TrashedAt == null && m.ProfileOfAvatarId == null).ExecuteFirstAsync(token);
+			if (attachment == default)
+				return NotFoundError();
+			if (attachment.PostId != null || attachment.ScheduledStatusId != null)
+				return Error(StatusCodes.Status422UnprocessableEntity, "Media attachment is currently used by a status");
+			await _media.Trash(m => m.ID == attachment.ID && m.PostId == null && m.ScheduledStatusId == null, "deleted by its owner", token);
+			return Json(new { });
+		}
+
 		// as on Mastodon, only media not posted yet: a posted one's description and focus change by editing its post (media_attributes)
 		[HttpPut("/api/v1/media/{id}"), Scope("write:media")]
 		public async Task<IActionResult> Update(string id, CancellationToken token)