feat: export Recharts theme preset for consuming apps

Add rechartsTheme config object that maps design tokens to Recharts
component props, ensuring visual consistency without adding Recharts
as a dependency. Also export CHART_COLORS, ChartSeries, and DataPoint
types for public use. Document charting strategy in COMPONENT_GUIDE.md.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -104,6 +104,10 @@ import { GlobalFilterProvider, useGlobalFilters } from '@cameleer/design-system'
 // Utils
 import { hashColor } from '@cameleer/design-system'
 
+// Recharts theme (for advanced charts — treemap, radar, heatmap, etc.)
+import { rechartsTheme, CHART_COLORS } from '@cameleer/design-system'
+import type { ChartSeries, DataPoint } from '@cameleer/design-system'
+
 // Styles (once, at app root)
 import '@cameleer/design-system/style.css'
 ```