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/web/pages/build_flutter_app.html

@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>Flutter web app not built</title>
+    <link rel="stylesheet" href="/web/css/style.css">
+  </head>
+  <body>
+    <div class="content">
+      <div class="logo-box">
+        <img src="/web/images/serverpod-logo.svg" width="160" style="margin-top: 8px; margin-bottom: 12px;">
+      </div>
+      <hr>
+      <div class="info-box">
+        <p style="margin-bottom: 12px; font-weight: 600; color: #333;">Flutter web app not built</p>
+        <p>
+          The production version of your Flutter web app has not yet been built. The app is automatically built before deploying to Serverpod Cloud. If you want to manually build it, run the following command:
+        </p>
+        <div style="background-color: #f5f5f5; padding: 12px; border-radius: 6px; margin-top: 12px; margin-bottom: 12px; font-family: 'Courier New', monospace; font-size: 13px; color: #333; overflow-x: auto;">
+          serverpod run flutter_build
+        </div>
+
+        <p>
+          After the app has been built, restart the server and revisit this page.
+        </p>
+      </div>
+      <hr>
+      <div class="link-box">
+        <a href="https://serverpod.dev">Serverpod</a>
+        •
+        <a href="https://docs.serverpod.dev">Get Started</a>
+        •
+        <a href="https://github.com/serverpod/serverpod">Github</a>
+      </div>
+    </div>
+  </body>
+</html>