build(app): the editor from its hosted fork

The app took the editor from our fork of AppFlowy Editor in a folder next to the
repository, which nobody else had, and which CI can't reach either. The fork now lives at
https://code.halkyon.app/project-halkyon/appflowy-editor (public; dual-licensed AGPL-3.0
or MPL-2.0 like upstream), on its branch halkyon/win32-v6, and the app depends on it by
git URL, pinned to the signed commit 0dac8a0. That commit adds `publish_to: none` to the
fork: it is a git dependency only, and the package name belongs to AppFlowy on pub.dev.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

pubspec.lock

@@ -52,9 +52,11 @@ packages:
   appflowy_editor:
     dependency: transitive
     description:
-      path: "../appflowy-editor"
-      relative: true
-    source: path
+      path: "."
+      ref: "0dac8a046e91ac89c0ffa13e2d603ebf50873332"
+      resolved-ref: "0dac8a046e91ac89c0ffa13e2d603ebf50873332"
+      url: "https://code.halkyon.app/project-halkyon/appflowy-editor.git"
+    source: git
     version: "6.1.0"
   archive:
     dependency: transitive