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/+page.server.ts

@@ -0,0 +1,36 @@
+import { error } from '@sveltejs/kit';
+import { createApiClient } from '$lib/api.server';
+import { getErrorMessage } from '$lib/errors';
+import type { PageServerLoad } from './$types';
+
+export const load: PageServerLoad = async ({ url, fetch }) => {
+	const api = createApiClient(fetch);
+	const personId = url.searchParams.get('personId') ?? undefined;
+	const documentId = url.searchParams.get('documentId') ?? undefined;
+
+	const [listResult, personResult] = await Promise.all([
+		api.GET('/api/geschichten', {
+			params: {
+				query: {
+					status: 'PUBLISHED',
+					personId,
+					documentId
+				}
+			}
+		}),
+		personId
+			? api.GET('/api/persons/{id}', { params: { path: { id: personId } } })
+			: Promise.resolve(null)
+	]);
+
+	if (!listResult.response.ok) {
+		const code = (listResult.error as unknown as { code?: string })?.code;
+		throw error(listResult.response.status, getErrorMessage(code));
+	}
+
+	return {
+		geschichten: listResult.data ?? [],
+		personFilter: personResult && personResult.response.ok ? personResult.data! : null,
+		documentFilter: documentId ?? null
+	};
+};