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/AccountsController.cs

@@ -181,6 +181,17 @@ namespace PrivaPub.Api.Mastodon.Controllers
 				? await search.Followed(MyId, Params.Get("q"), Limit(), token)
 				: await search.Find(Params.Get("q"), Params.Bool("resolve") == true && MyId != default, Limit(), token));
 
+		// Mastodon 4.3: several accounts at once (at most 40), those that exist, in no promised order
+		[HttpGet("/api/v1/accounts"), Scope("read:accounts", requiresUser: false), Microsoft.AspNetCore.Authorization.AllowAnonymous]
+		public async Task<IActionResult> Many(CancellationToken token)
+		{
+			var accounts = new List<object>();
+			foreach (var id in Params.List("id").Distinct().Take(40))
+				if (await _mapper.Account(id, token) is { } account)
+					accounts.Add(account);
+			return Json(accounts);
+		}
+
 		[HttpGet("/api/v1/accounts/{id}"), Scope("read:accounts", requiresUser: false), Microsoft.AspNetCore.Authorization.AllowAnonymous]
 		public async Task<IActionResult> Get(string id, CancellationToken token)
 		{