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/radio.json

@@ -0,0 +1,15 @@
+{
+  "radio": {
+    "$description": "Radio component tokens — single-select control for mutually exclusive options. Used in service selection, payment method, and arrangement forms.",
+    "size": {
+      "$type": "dimension",
+      "$description": "Radio button outer circle size.",
+      "default": { "$value": "20px", "$description": "Default radio size — matches Figma 16px + padding for 44px touch target area" }
+    },
+    "dotSize": {
+      "$type": "dimension",
+      "$description": "Inner dot size when selected.",
+      "default": { "$value": "10px", "$description": "Selected indicator dot — 50% of outer size" }
+    }
+  }
+}