feat: update components for multi-user support

- Add sharing indicator to ListCard showing collaborator count
- Add permission badge and share button to ListDetailView
- Disable editing in ItemForm for viewers with visual feedback
- Add permission checks to item detail and edit pages
- Hide edit/delete buttons for viewers on item detail page
- Pass permission and collaborator data through component hierarchy
- Update navigation to include profile and invitations links (already done in previous tasks)

Implements task 15 from user-auth-and-sharing spec

.kiro/specs/user-auth-and-sharing/tasks.md

@@ -208,7 +208,7 @@
   - Add invitations page
   - _Requirements: 5.1, 5.4, 8.1, 8.2_
 
-- [-] 14. Implement profile management
+- [x] 14. Implement profile management
   - Create profile page and ProfileForm component
   - Implement updateProfile server action
   - Create PasswordChangeForm component
@@ -236,7 +236,7 @@
   - **Property 29: Profile data exposure protection**
   - **Validates: Requirements 7.5**
 
-- [ ] 15. Update existing components for multi-user
+- [x] 15. Update existing components for multi-user
   - Modify ListCard to show sharing indicator
   - Update ListDetailView with share button and permission display
   - Modify ItemForm to disable editing for viewers