feat(geschichten): add /geschichten routes (index, detail, new, edit)

- /geschichten — published-stories index with filter pills + "+ Neue Geschichte"
  for BLOG_WRITERs; supports ?personId and ?documentId pre-filtering
- /geschichten/[id] — reader detail with sanitised {@html} body, person and
  document chip sections, BLOG_WRITER edit/delete with confirm dialog
- /geschichten/new — editor with optional ?personId and ?documentId pre-fill
  (silent ignore on unknown IDs to avoid leaking entity existence)
- /geschichten/[id]/edit — editor populated from existing story; BLOG_WRITE
  guard redirects readers to the detail page

All routes load via createApiClient(fetch) with !response.ok error handling
following the project pattern; PATCH/DELETE go through raw fetch which the
Vite dev proxy / Caddy production proxy authenticates via cookie.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -0,0 +1,20 @@
+import { error, redirect } from '@sveltejs/kit';
+import { createApiClient } from '$lib/api.server';
+import { getErrorMessage } from '$lib/errors';
+import type { PageServerLoad } from './$types';
+
+export const load: PageServerLoad = async ({ params, fetch, parent }) => {
+	const layout = await parent();
+	if (!layout.canBlogWrite) {
+		throw redirect(303, `/geschichten/${params.id}`);
+	}
+	const api = createApiClient(fetch);
+	const result = await api.GET('/api/geschichten/{id}', {
+		params: { path: { id: params.id } }
+	});
+	if (!result.response.ok) {
+		const code = (result.error as unknown as { code?: string })?.code;
+		throw error(result.response.status, getErrorMessage(code));
+	}
+	return { geschichte: result.data! };
+};