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>

src/App.tsx

@@ -2,8 +2,8 @@ import React, { useState, useEffect, useCallback, useMemo, ReactNode, lazy, Susp
 import { BrowserRouter as Router, Routes, Route, Link, useLocation } from 'react-router-dom';
 
 const Settings = lazy(() => import('./components/Settings'));
-const PeriodSelectorDemo = lazy(() => import('./components/PeriodSelectorDemo'));
-const DashboardDemo = lazy(() => import('./components/DashboardDemo'));
+const Comparison = lazy(() => import('./components/Comparison'));
+const Dashboard = lazy(() => import('./components/Dashboard'));
 import Login from './components/Login';
 import LoadingSkeleton from './components/shared/LoadingSkeleton';
 import { fetchData, getCacheStatus, refreshData, getUniqueMuseums, getUniqueChannels } from './services/dataService';
@@ -301,8 +301,8 @@ function App() {
         <main>
           <Suspense fallback={<LoadingSkeleton />}>
             <Routes>
-              <Route path="/"           element={<DashboardDemo data={data} seasons={seasons} includeVAT={includeVAT} setIncludeVAT={setIncludeVAT} allowedMuseums={allowedMuseums} allowedChannels={allowedChannels} />} />
-              <Route path="/comparison" element={<PeriodSelectorDemo data={data} seasons={seasons} includeVAT={includeVAT} allowedMuseums={allowedMuseums} allowedChannels={allowedChannels} />} />
+              <Route path="/"           element={<Dashboard data={data} seasons={seasons} includeVAT={includeVAT} setIncludeVAT={setIncludeVAT} allowedMuseums={allowedMuseums} allowedChannels={allowedChannels} />} />
+              <Route path="/comparison" element={<Comparison data={data} seasons={seasons} includeVAT={includeVAT} allowedMuseums={allowedMuseums} allowedChannels={allowedChannels} />} />
               {userRole === 'admin' && <Route path="/settings" element={<Settings onSeasonsChange={loadSeasons} allMuseums={allMuseumsList} allChannels={allChannelsList} />} />}
             </Routes>
           </Suspense>