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-types/src/contact.ts

@@ -0,0 +1,80 @@
+/**
+ * Contact-related types for cross-app integration
+ *
+ * These types are used when referencing contacts from the Contacts app
+ * in other apps like Todo and Calendar.
+ */
+
+/**
+ * Reference to a contact with cached display data.
+ * Used for offline display when Contacts API is unavailable.
+ */
+export interface ContactReference {
+	/** Contact ID from Contacts app */
+	contactId: string;
+	/** Cached display name */
+	displayName: string;
+	/** Cached email */
+	email?: string;
+	/** Cached photo URL */
+	photoUrl?: string;
+	/** Cached company name */
+	company?: string;
+	/** ISO timestamp when data was fetched (for cache invalidation) */
+	fetchedAt: string;
+}
+
+/**
+ * Summary of a contact from the Contacts API.
+ * Contains essential fields for display in selectors and lists.
+ */
+export interface ContactSummary {
+	id: string;
+	displayName: string;
+	firstName?: string;
+	lastName?: string;
+	email?: string;
+	phone?: string;
+	company?: string;
+	photoUrl?: string;
+}
+
+/**
+ * Manual contact entry (when contact doesn't exist in Contacts app).
+ * Used for calendar attendees who aren't in the user's contacts.
+ */
+export interface ManualContactEntry {
+	/** Email address (required for manual entries) */
+	email: string;
+	/** Display name (optional) */
+	name?: string;
+	/** Indicates this is a manual entry, not from Contacts app */
+	isManual: true;
+}
+
+/**
+ * Union type for contact references that can be either
+ * a real contact or a manual entry.
+ */
+export type ContactOrManual = ContactReference | ManualContactEntry;
+
+/**
+ * Helper to check if a contact entry is manual
+ */
+export function isManualContact(contact: ContactOrManual): contact is ManualContactEntry {
+	return 'isManual' in contact && contact.isManual === true;
+}
+
+/**
+ * Helper to create a ContactReference from a ContactSummary
+ */
+export function createContactReference(contact: ContactSummary): ContactReference {
+	return {
+		contactId: contact.id,
+		displayName: contact.displayName,
+		email: contact.email,
+		photoUrl: contact.photoUrl,
+		company: contact.company,
+		fetchedAt: new Date().toISOString(),
+	};
+}

packages/shared-types/src/index.ts

@@ -16,6 +16,9 @@ export * from './ui';
 // Common utility types
 export * from './common';
 
+// Contact types for cross-app integration
+export * from './contact';
+
 // API types
 export interface User {
 	id: string;