feat(contacts): integrate contacts into Todo and Calendar apps

- Add ContactSelector, ContactBadge, ContactAvatar to shared-ui
- Add ContactsClient API service to shared-auth
- Add ContactReference, ContactSummary types to shared-types
- Todo: Add assignee and involvedContacts to tasks with UI in TaskEditModal
- Todo: Display contacts in TaskItem and KanbanTaskCard
- Calendar: Add AttendeeSelector with RSVP status support
- Calendar: Integrate attendees in EventForm
- Calendar: Add task drag-drop to calendar views (Day/Week/MultiDay)
- Contacts: Add ContactTasks component to show related tasks
- Backend: Add findByContact endpoint to Todo task service
- UI polish: glassmorphism styling, keyboard navigation, auto-focus

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/shared-auth/src/index.ts

@@ -70,6 +70,10 @@ export {
 } from './interceptors/fetchInterceptor';
 export type { FetchInterceptorConfig } from './interceptors/fetchInterceptor';
 
+// Contacts client for cross-app integration
+export { ContactsClient, createContactsClient } from './clients/contactsClient';
+export type { ContactsClientConfig, ContactSearchOptions } from './clients/contactsClient';
+
 /**
  * Initialize auth service with all adapters for web
  *