feat: integrate insurance coverage management for clinic services

- Updated NewSessionPage to calculate patient share based on insurance coverage rules.
- Refactored billing calculations to utilize new patientShareOf function for service items.
- Enhanced API documentation to reflect changes in service coverage structure.
- Implemented ServiceInsuranceModal for managing insurance coverage per service.
- Added UI components for displaying and editing insurance coverage details.
- Removed obsolete toggle switch styles and adjusted CSS for new components.
- Ensured backend endpoints support both service_item_id and service_item_uuid for flexibility.

assets/admin/components/ui/SearchableSelect.tsx

@@ -42,7 +42,7 @@ export default function SearchableSelect({
   const styles: StylesConfig<SelectOption, false, GroupBase<SelectOption>> = {
     control: (base, state) => ({
       ...base,
-      background:   darkMode ? 'var(--surface)' : 'var(--surface)',
+      background:   state.isFocused ? 'var(--surface)' : 'var(--surface-2)',
       borderColor:  state.isFocused ? 'var(--primary)' : 'var(--border)',
       boxShadow:    state.isFocused ? '0 0 0 4px var(--ring)' : 'none',
       borderRadius: 'var(--r-sm)',