feat: add address book directories with drag-and-drop and editor picker

- Show address books in sidebar organized by personal directories and
  shared accounts, replacing the flat shared accounts list
- Make contact list items draggable with multi-select support using
  native HTML5 drag-and-drop (application/x-contact-ids MIME type)
- Add drop targets on sidebar address book items with visual feedback
- Add moveContactToAddressBook store method supporting same-account
  updates and cross-account create+delete moves
- Add address book picker dropdown in contact create/edit form
- Update ContactCategory type from sharedAccountId to addressBookId
- Add address_books translations to all 8 locales
- Fix contact-list-item tests for new selectedContactIds prop

components/contacts/__tests__/contact-list-item.test.tsx

@@ -30,6 +30,7 @@ describe('ContactListItem', () => {
     density: 'regular' as const,
     onClick: vi.fn(),
     onCheckboxClick: vi.fn(),
+    selectedContactIds: new Set<string>(),
   };
 
   it('renders contact name and email', () => {