Add Switch and Radio atom components

Switch:
- Wraps MUI Switch with FA brand tokens
- Bordered pill track (Figma Style One), brand.500 fill when active
- 4 component tokens: track width/height/borderRadius, thumb size
- Stories include interactive service add-ons demo

Radio:
- Wraps MUI Radio with FA brand tokens
- Brand.500 fill when selected, neutral.400 unchecked
- 2 component tokens: outer size, dot size
- Stories include card selection and payment method patterns

Also:
- Added ColourToggle and Slider to component registry (deferred)
- Updated token registry and session log

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

src/components/atoms/Switch/index.ts

@@ -0,0 +1,2 @@
+export { Switch, default } from './Switch';
+export type { SwitchProps } from './Switch';