phsl / new-api

- DashboardHeader.jsx: replace Semi's IconSearch/IconRefresh with lucide-react's Search/RefreshCw (size 16), preserve existing button styles
- UptimePanel.jsx: replace Semi's IconRefresh with lucide-react's RefreshCw (size 14), keep styling intact
- UserArea.jsx: replace Semi's IconChevronDown with lucide-react's ChevronDown (size 14), preserve visual parity
- Update imports: remove @douyinfe/semi-icons usage where replaced; add lucide-react imports
- Verified no remaining IconSearch/IconRefresh in dashboard; no new linter errors

Motivation: unify icon library for core actions and improve UI consistency.
Follow-ups: consider migrating remaining Semi icons (e.g., plus/minus, charts) to lucide-react.