test(admin): cover all admin/system status branches

Adds backfill success banner, RUNNING import-status rendering,
DONE import-status with processed count, FAILED thumbnail-status
with error message, DONE thumbnail-status with retry button.

5 new tests covering state-machine branches.

Refs #496.

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

frontend/src/routes/admin/system/page.svelte.test.ts

@@ -110,4 +110,132 @@ describe('admin/system page', () => {
 		expect(calls.some((c) => c.includes('import-status'))).toBe(true);
 		expect(calls.some((c) => c.includes('thumbnail-status'))).toBe(true);
 	});
+
+	it('shows the success banner after backfill versions completes', async () => {
+		fetchSpy.mockImplementation(async (url: RequestInfo | URL) => {
+			const u = url.toString();
+			if (u.includes('backfill-versions')) {
+				return new Response(JSON.stringify({ count: 12 }), {
+					status: 200,
+					headers: { 'Content-Type': 'application/json' }
+				});
+			}
+			return new Response(JSON.stringify({ state: 'IDLE' }), {
+				status: 200,
+				headers: { 'Content-Type': 'application/json' }
+			});
+		});
+
+		render(AdminSystemPage, { props: {} });
+
+		const btn = (await page
+			.getByRole('button', { name: /jetzt auffüllen/i })
+			.element()) as HTMLButtonElement;
+		btn.click();
+
+		await new Promise((r) => setTimeout(r, 100));
+		const banner = document.querySelector('.bg-green-50');
+		expect(banner).not.toBeNull();
+	});
+
+	it('renders the running state for import-status', async () => {
+		fetchSpy.mockImplementation(async (url: RequestInfo | URL) => {
+			const u = url.toString();
+			if (u.includes('import-status')) {
+				return new Response(
+					JSON.stringify({ state: 'RUNNING', message: '', processed: 0, startedAt: null }),
+					{ status: 200, headers: { 'Content-Type': 'application/json' } }
+				);
+			}
+			return new Response(JSON.stringify({ state: 'IDLE' }), {
+				status: 200,
+				headers: { 'Content-Type': 'application/json' }
+			});
+		});
+
+		render(AdminSystemPage, { props: {} });
+
+		await new Promise((r) => setTimeout(r, 100));
+		expect(document.body.textContent).toMatch(/läuft|wird ausgeführt/i);
+	});
+
+	it('renders the DONE state with processed count for import-status', async () => {
+		fetchSpy.mockImplementation(async (url: RequestInfo | URL) => {
+			const u = url.toString();
+			if (u.includes('import-status')) {
+				return new Response(
+					JSON.stringify({ state: 'DONE', message: '', processed: 99, startedAt: null }),
+					{ status: 200, headers: { 'Content-Type': 'application/json' } }
+				);
+			}
+			return new Response(JSON.stringify({ state: 'IDLE' }), {
+				status: 200,
+				headers: { 'Content-Type': 'application/json' }
+			});
+		});
+
+		render(AdminSystemPage, { props: {} });
+
+		await new Promise((r) => setTimeout(r, 100));
+		expect(document.body.textContent).toContain('99');
+	});
+
+	it('renders the FAILED state with the error message for thumbnail-status', async () => {
+		fetchSpy.mockImplementation(async (url: RequestInfo | URL) => {
+			const u = url.toString();
+			if (u.includes('thumbnail-status')) {
+				return new Response(
+					JSON.stringify({
+						state: 'FAILED',
+						message: 'connection refused',
+						total: 0,
+						processed: 0,
+						skipped: 0,
+						failed: 0,
+						startedAt: null
+					}),
+					{ status: 200, headers: { 'Content-Type': 'application/json' } }
+				);
+			}
+			return new Response(JSON.stringify({ state: 'IDLE' }), {
+				status: 200,
+				headers: { 'Content-Type': 'application/json' }
+			});
+		});
+
+		render(AdminSystemPage, { props: {} });
+
+		await new Promise((r) => setTimeout(r, 100));
+		expect(document.body.textContent).toContain('connection refused');
+	});
+
+	it('renders the DONE state for thumbnail-status with retry button', async () => {
+		fetchSpy.mockImplementation(async (url: RequestInfo | URL) => {
+			const u = url.toString();
+			if (u.includes('thumbnail-status')) {
+				return new Response(
+					JSON.stringify({
+						state: 'DONE',
+						message: '',
+						total: 100,
+						processed: 95,
+						skipped: 3,
+						failed: 2,
+						startedAt: null
+					}),
+					{ status: 200, headers: { 'Content-Type': 'application/json' } }
+				);
+			}
+			return new Response(JSON.stringify({ state: 'IDLE' }), {
+				status: 200,
+				headers: { 'Content-Type': 'application/json' }
+			});
+		});
+
+		render(AdminSystemPage, { props: {} });
+
+		await new Promise((r) => setTimeout(r, 100));
+		const banner = document.querySelector('[data-testid="thumbnails-status-done"]');
+		expect(banner).not.toBeNull();
+	});
 });