Fix Docker build issues

- Remove unused formatLocalTimeOnly import from App.js
- Add client/build to .dockerignore to prevent stale build artifacts
- Ensures clean Docker builds without local build cache conflicts

.dockerignore

@@ -13,4 +13,5 @@ coverage
 .next
 out
 client/node_modules
+client/build
 server/node_modules

client/src/App.js

@@ -6,7 +6,7 @@ import './App.css';
 import SettingsWizard from './SettingsWizard';
 import History from './History';
 import SLA from './SLA';
-import { formatLocalTime, formatLocalTimeOnly, formatChartTime } from './utils/timeUtils';
+import { formatLocalTime, formatChartTime } from './utils/timeUtils';
 
 function Dashboard() {
   const [resources, setResources] = useState([]);