R7 custom emoji in decePub: the server's own, administered, picked, suggested and shown

Administration has a Custom emoji section (EmojiPanel, data-admin-section=emoji): the server's emoji by category, added
with a picture streamed from the file, changed (category, picker, disabled, picture; never the shortcode) and deleted,
asked first, with PrivaPub's 409 and 422 in the dialog. EmojiService reads /clientapi/admin/emoji and, for everyone,
/api/v1/custom_emojis, kept a day in localStorage (CustomEmojiCache) and read again after a change here. EmojiPicker
(a DDropdown sheet on a phone, rendered only while open) offers them by category with common unicode emoji, searchable:
the composer writes the choice at the caret, a card and the announcements banner react with it. The composer suggests
custom emoji after `:` and two letters. Custom reactions toggle as :shortcode: and show their picture, notifications of
one too; located posts, announcements and NavMenu's persona names render the server's emoji.

Verified: Release build, 0 errors (the 3 warnings were there before). Not run against PrivaPub or in the pasture.

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

Services/AnnouncementService.cs

@@ -10,7 +10,8 @@ namespace decePubClient.Services
 {
 	/// <summary>
 	/// The administrators' announcements as the current persona reads them (/api/v1/announcements): the ones shown now,
-	/// dismissed one by one, and reacted to with a unicode emoji (eight different ones at most on each). Dismissals and
+	/// dismissed one by one, and reacted to with a unicode emoji or one of the server's custom emoji (eight different ones at
+	/// most on each). Dismissals and
 	/// reactions are the persona's own and never leave PrivaPub; the stream tells of new, changed and removed ones
 	/// (StreamingService.Announced). The administrators write them through InstanceAdminService.
 	/// </summary>
@@ -35,7 +36,8 @@ namespace decePubClient.Services
 			return response.IsSuccessStatusCode ? new WebResult() : await response.Content.ReadWebResult(response.StatusCode, localizer, cancellationToken);
 		}
 
-		/// <summary>Adds the persona's reaction, or takes it back; PrivaPub refuses anything but one unicode emoji (422).</summary>
+		/// <summary>Adds the persona's reaction, or takes it back: one unicode emoji, or one of the server's custom emoji by its
+		/// shortcode (with its colons or without); PrivaPub refuses anything else (422).</summary>
 		public async Task<WebResult> React(string announcementId, string emoji, bool add, CancellationToken cancellationToken = default)
 		{
 			var route = APIs.Mastodon.M_AnnouncementReaction(announcementId, emoji);