feat(edit): unify edit page with enrich split-panel layout

Extract DocumentEditLayout shared component for the PDF+form split-panel
UI, replacing the old scrolling layout on /documents/[id]/edit with the
same fixed-panel structure used by /enrich/[id]. Removes TranscriptionSection
and FileSectionEdit from the edit page; file upload/replace is now handled
by the shared layout. Delete SaveBar and FileSectionEdit as dead code.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/documents/[id]/edit/+page.server.ts

@@ -6,12 +6,15 @@ import { parseBackendError, getErrorMessage } from '$lib/errors';
 export async function load({
 	params,
 	fetch,
-	locals
+	locals,
+	depends
 }: {
 	params: { id: string };
 	fetch: typeof globalThis.fetch;
 	locals: App.Locals;
+	depends: (dep: string) => void;
 }) {
+	depends('app:document');
 	const canWrite =
 		locals.user?.groups?.some((g: { permissions: string[] }) =>
 			g.permissions.includes('WRITE_ALL')