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

Models/CustomEmojiCache.cs

@@ -0,0 +1,14 @@
+using decePubClient.Models.Mastodon;
+
+namespace decePubClient.Models;
+
+/// <summary>
+/// The server's custom emoji its picker offers (/api/v1/custom_emojis), as EmojiService last read them: kept in
+/// localStorage under its type name and used for a day, then read again (at once after an administrator changes one in
+/// this client).
+/// </summary>
+public class CustomEmojiCache
+{
+	public DateTime FetchedAt { get; set; }
+	public List<CustomEmoji> Emojis { get; set; } = [];
+}