feat(frontend): update generated API types and Geschichte routes for JourneyItem model

- api.ts: add GeschichteType, JourneyItem, GeschichteSummary schemas;
  remove documentId param from list endpoint; change list response to
  GeschichteSummary[]; add type + items to Geschichte; remove documents field
- GeschichteEditor: remove DocumentMultiSelect + documentIds from payload
  (journey items are managed via the future Lesereisen editor, not here)
- GET /geschichten page: remove documentId filter from server load + URL logic
- geschichten/new: remove documentId pre-population from server load
- geschichten/[id]: replace g.documents with g.items (document-backed JourneyItems)
- geschichten/new + [id]/edit: remove documentIds from submit payload type

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

frontend/src/routes/geschichten/[id]/+page.svelte

@@ -96,25 +96,20 @@ async function handleDelete() {
 		</section>
 	{/if}
 
-	<!-- Dokumente -->
-	{#if g.documents && g.documents.length > 0}
+	<!-- Dokumente (JourneyItems) -->
+	{#if g.items && g.items.some((i) => i.documentId)}
 		<section class="mt-8 border-t border-line pt-6">
 			<h2 class="mb-3 font-sans text-xs font-bold tracking-widest text-ink-2 uppercase">
 				{m.geschichten_documents_section()}
 			</h2>
 			<ul class="flex flex-col gap-2">
-				{#each g.documents as d (d.id)}
+				{#each g.items.filter((i) => i.documentId) as item (item.id)}
 					<li>
 						<a
-							href="/documents/{d.id}"
+							href="/documents/{item.documentId}"
 							class="block rounded border border-line bg-surface px-4 py-3 font-serif text-base text-ink hover:bg-muted"
 						>
-							{d.title}
-							{#if d.documentDate}
-								<span class="ml-2 font-sans text-xs text-ink-3">
-									{formatDate(d.documentDate, 'short')}
-								</span>
-							{/if}
+							{item.note ?? item.documentId}
 						</a>
 					</li>
 				{/each}

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

@@ -17,7 +17,6 @@ async function handleSubmit(payload: {
 	body: string;
 	status: 'DRAFT' | 'PUBLISHED';
 	personIds: string[];
-	documentIds: string[];
 }) {
 	submitting = true;
 	errorMessage = null;