refactor: rename Demo components to canonical names and purge dead code

- DashboardDemo → Dashboard, PeriodSelectorDemo → Comparison (these were the real active routes)
- Delete old Dashboard, Comparison, NavDemo, Slides, ChartExport (replaced / unused)
- Delete 8 unused shared components: DateRangePicker, PeriodPicker, FilterControls, MultiSelect, Carousel, ChartCard, EmptyState, StatCard, ToggleSwitch
- Fix date picker stay-open behavior: selections now update draft state only; Apply/Cancel buttons commit or discard
- shared/index.tsx now only exports LoadingSkeleton

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

server/src/routes/erp.ts

@@ -1,5 +1,6 @@
 import { Router, Request, Response } from 'express';
 import { fetchSales, isConfigured } from '../services/erpClient';
+import { etl } from '../config';
 
 const router = Router();