Load page.json by import, publish via fs, drop cookie auth

The editor no longer round-trips through /api/pages. Each route's
editor/page.tsx imports its own `../page.json` and hands it to
PageEditor as a prop, so the editor opens with the page already in
hand — no fetch, no loading state, no undo history seeded from a
placeholder. Globals still come from app.globals.json.

Publishing moves from `PUT /api/pages` to a `publishPage` server
action that writes the route's page.json with node:fs directly.
The target path is still built from the lib/pages.ts registry rather
than from the caller, so an unknown route key is rejected instead of
escaping app/.

Removes the customer account auth entirely: the httpOnly cookie
session, the /api/account/* handlers, the customer service and
GraphQL documents, the account-* blocks, and the /account/* routes.
The template has no auth, so nothing reads a cookie now.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01STGDvL4X7FhHHnxdRE2ayo

app/collections/[handle]/editor/page.tsx

@@ -1,7 +1,9 @@
 import PageEditor from '@/components/page-editor';
+import pageData from '../page.json';
 
 // Editor for /collections/[handle]. Sitting under the route it edits means the preview
-// resolves the same params the public page gets.
+// resolves the same params the public page gets, and `../page.json` is the
+// very file publishing writes back to.
 export default function EditorPage() {
-  return <PageEditor routeKey="/collections/[handle]" />;
+  return <PageEditor routeKey="/collections/[handle]" page={pageData} />;
 }

app/collections/editor/page.tsx

@@ -1,7 +1,9 @@
 import PageEditor from '@/components/page-editor';
+import pageData from '../page.json';
 
 // Editor for /collections. Sitting under the route it edits means the preview
-// resolves the same params the public page gets.
+// resolves the same params the public page gets, and `../page.json` is the
+// very file publishing writes back to.
 export default function EditorPage() {
-  return <PageEditor routeKey="/collections" />;
+  return <PageEditor routeKey="/collections" page={pageData} />;
 }