test(dashboard): add missing tag tree mock to recentDocs reader test

The sequential mock chain in the recentDocs test was missing a 6th call
for /api/tags/tree added in the tag tree fetch. Without it the mock
returned undefined, causing settled() to throw and the outer catch to
return an empty recentDocs array.

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

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

@@ -421,7 +421,8 @@ describe('home page load — reader branch (isReader = !canWrite && !canAnnotate
 				response: { ok: true },
 				data: { items: [searchItem], totalElements: 1, pageNumber: 0, pageSize: 5, totalPages: 1 }
 			}) // search
-			.mockResolvedValueOnce({ response: { ok: true }, data: [] }); // stories
+			.mockResolvedValueOnce({ response: { ok: true }, data: [] }) // stories
+			.mockResolvedValueOnce({ response: { ok: true }, data: [] }); // tags/tree
 		vi.mocked(createApiClient).mockReturnValue({ GET: mockGet } as ReturnType<
 			typeof createApiClient
 		>);