refactor: use CustomTextInput in login and register screens

- Replace raw TextInput with CustomTextInput in login and register
  for consistent focus border effect across the app
- Add placeholder, secureTextEntry, autoCapitalize, keyboardType
  props to CustomTextInput
- Remove hardcoded default padding (px-3 py-2) and h-11/12 from
  CustomTextInput, callers now set padding via className
- Add explicit px-3 py-2 to existing callers (settings, editEvent)
- Update CLAUDE.md with new CustomTextInput usage and props

apps/client/src/app/(tabs)/settings.tsx

@@ -44,7 +44,7 @@ const CaldavTextInput = ({
     <View className="flex flex-row items-center py-1">
       <Text className="ml-4 w-24">{title}:</Text>
       <CustomTextInput
-        className="flex-1 mr-4"
+        className="flex-1 mr-4 px-3 py-2"
         text={value}
         onValueChange={onValueChange}
       />