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_server/README.md

@@ -0,0 +1,10 @@
+# halkyon_todo_server
+
+This is the starting point for your Serverpod server.
+
+Start your server by running:
+
+    cd halkyon_todo
+    serverpod start
+
+When you are finished, you can shut down the running server with `Q`.