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>

tokens/component/switch.json

@@ -0,0 +1,17 @@
+{
+  "switch": {
+    "$description": "Switch component tokens — toggle control for enabling/disabling options. Used in arrangement forms for add-on services.",
+    "track": {
+      "$type": "dimension",
+      "$description": "Switch track dimensions.",
+      "width": { "$value": "44px", "$description": "Track width — slightly narrower than Figma 52px for better proportion with 44px touch target" },
+      "height": { "$value": "24px", "$description": "Track height" },
+      "borderRadius": { "$value": "{borderRadius.full}", "$description": "Pill shape" }
+    },
+    "thumb": {
+      "$type": "dimension",
+      "$description": "Switch thumb (knob) dimensions.",
+      "size": { "$value": "18px", "$description": "Thumb diameter — sits inside the track with 3px inset" }
+    }
+  }
+}