Implement the four core frontend pages for the DAK Zweitmeinungs-Portal:
- DashboardPage: KPI cards, weekly stacked bar chart, fallgruppen donut chart, year selector
- CasesPage: filterable/searchable paginated table with detail slide-out and inline ICD editing
- ImportPage: CSV upload with preview/confirm, ICD Excel upload, import history log
- IcdPage: reuses CasesPage with pending-icd-only filter
Also adds shadcn/ui components (table, select, tabs, skeleton, scroll-area) and
new TypeScript types for import log and ICD import responses.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
