feat(core): edit icon in navigation panel (#13595)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Rename dialog now edits per-item explorer icons (emoji or custom) and
can skip name-change callbacks. Doc icon picker added to the editor with
localized "Add icon" placeholder and readonly rendering. Icon editor
supports fallbacks, trigger variants, and improved input/test-id wiring.

- **Style**
- Updated icon picker and trigger sizing and placeholder visuals;
title/icon layout adjustments.

- **Chores**
- Explorer icon storage and module added to persist and serve icons
across the app.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/utils/extract-emoji-icon.ts

@@ -2,6 +2,9 @@ import Graphemer from 'graphemer';
 const emojiRe =
   /(\u00a9|\u00ae|[\u2000-\u3300]|\ud83c[\ud000-\udfff]|\ud83d[\ud000-\udfff]|\ud83e[\ud000-\udfff])/g;
 
+/**
+ * @deprecated use ExplorerIconService instead
+ */
 export function extractEmojiIcon(text: string) {
   emojiRe.lastIndex = 0;
   const match = emojiRe.exec(text);