feat(sync): show sync changes in banner and details dialog

src/pages/Dashboard.test.jsx

@@ -17,6 +17,7 @@ const quietRoutes = {
     'GET /api/library/summary': json(200, empty),
     'GET /api/hints': json(200, {results: []}),
     'GET /api/news': json(200, {results: []}),
+    'GET /api/library/sync-changes': json(204, {}),
 };
 
 // Every request of the page with a Steam ID; the test of the 401 answers all but the user with 401.