chore: Halkyon Todo's scaffold joins the repository in apps/todo

Its server, client and app as `serverpod create` made them, with the
switch to server-side sessions that was waiting uncommitted, as files:
its one commit holds the scaffold alone.

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

apps/todo/halkyon_todo_flutter/assets/config.json

@@ -0,0 +1,3 @@
+{
+    "apiUrl": "http://localhost:8080"
+}