feat(shared-ui): add unified statistics components with theme support

- Add reusable chart components in shared-ui (StatsGrid, ActivityHeatmap, TrendLineChart, DonutChart, ProgressBars, StatisticsSkeleton)
- Use CSS variables (--primary) for consistent theme-based styling
- Add statistics pages to Calendar and Contacts apps
- Add statistics stores with app-specific metrics
- Fix PriorityDonutChart layout in Todo app (vertical layout with 2x2 legend grid)
- Add date-fns dependency to shared-ui

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/shared-ui/src/index.ts

@@ -110,3 +110,22 @@ export type { CommandBarItem, QuickAction, CreatePreview } from './command-bar';
 
 // Pages
 export { default as AppsPage } from './pages/AppsPage.svelte';
+
+// Charts - Statistics Visualization
+export {
+	StatsGrid,
+	ActivityHeatmap,
+	TrendLineChart,
+	DonutChart,
+	ProgressBars,
+	StatisticsSkeleton,
+	STAT_VARIANT_COLORS,
+} from './charts';
+export type {
+	StatVariant,
+	StatItem,
+	HeatmapDataPoint,
+	TrendDataPoint,
+	DonutSegment,
+	ProgressItem,
+} from './charts';