feat(documents): show global undated count chip on the filter toggle

Surface the backend's global undatedCount on the "Nur undatierte" toggle as
a count chip — the total undated documents matching the current filter
across all pages, not the page slice. The loader forwards undatedCount
straight through (defaulting to 0); the chip hides at 0 and stays visible
regardless of the toggle state so it advertises the triage backlog size.

generate:api was hand-edited (undatedCount added to DocumentSearchResult) —
CI must re-run npm run generate:api to confirm parity.

Refs #668

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

frontend/src/routes/documents/+page.server.ts

@@ -85,6 +85,7 @@ export async function load({ url, fetch }) {
 			pageNumber: 0,
 			pageSize: PAGE_SIZE,
 			totalPages: 0,
+			undatedCount: 0,
 			q,
 			from,
 			to,
@@ -116,6 +117,8 @@ export async function load({ url, fetch }) {
 		pageNumber: result.data?.pageNumber ?? page,
 		pageSize: result.data?.pageSize ?? PAGE_SIZE,
 		totalPages: result.data?.totalPages ?? 0,
+		// Global undated count for the active filter, across all pages (issue #668).
+		undatedCount: result.data?.undatedCount ?? 0,
 		q,
 		from,
 		to,

frontend/src/routes/documents/+page.svelte

@@ -268,6 +268,7 @@ $effect(() => {
 		bind:tagQ={tagQ}
 		bind:tagOperator={tagOperator}
 		bind:undated={undated}
+		undatedCount={data.undatedCount ?? 0}
 		initialSenderName={initialSenderName}
 		initialReceiverName={initialReceiverName}
 		navKey={navKey}

frontend/src/routes/documents/page.server.spec.ts

@@ -225,6 +225,51 @@ describe('documents page load — search params', () => {
 		expect(result.totalElements).toBe(42);
 	});
 
+	it('forwards the global undatedCount from the search result (#668)', async () => {
+		// The backend returns the global undated total for the active filter across
+		// ALL pages; the loader must pass it straight through, not recompute it locally.
+		const mockGet = vi.fn().mockResolvedValue({
+			response: { ok: true, status: 200 },
+			data: {
+				items: [],
+				totalElements: 200,
+				pageNumber: 0,
+				pageSize: 50,
+				totalPages: 4,
+				undatedCount: 73
+			}
+		});
+		vi.mocked(createApiClient).mockReturnValue({ GET: mockGet } as ReturnType<
+			typeof createApiClient
+		>);
+
+		const result = await load({
+			url: makeUrl({ q: 'test' }),
+			request: new Request('http://localhost/documents'),
+			fetch: vi.fn() as unknown as typeof fetch
+		});
+
+		expect(result.undatedCount).toBe(73);
+	});
+
+	it('defaults undatedCount to 0 when the search result omits it', async () => {
+		const mockGet = vi.fn().mockResolvedValue({
+			response: { ok: true, status: 200 },
+			data: { items: [], totalElements: 0, pageNumber: 0, pageSize: 50, totalPages: 0 }
+		});
+		vi.mocked(createApiClient).mockReturnValue({ GET: mockGet } as ReturnType<
+			typeof createApiClient
+		>);
+
+		const result = await load({
+			url: makeUrl(),
+			request: new Request('http://localhost/documents'),
+			fetch: vi.fn() as unknown as typeof fetch
+		});
+
+		expect(result.undatedCount).toBe(0);
+	});
+
 	it('returns filter values in the result for pre-filling the UI', async () => {
 		const mockGet = vi.fn().mockResolvedValue({
 			response: { ok: true, status: 200 },