feat(compose): sort address autocomplete by most recently used

Add ORDER BY receivedAt DESC to the searchAddresses query so the first
unique occurrence of each address comes from the newest email. Contacts
from recent conversations float to the top of the suggestions list.

Add a unit test verifying the sort order.

Fixes #83

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/data/repositories/email_repository_impl.dart

@@ -2614,6 +2614,7 @@ class EmailRepositoryImpl implements EmailRepository {
                     t.ccJson.like(pattern));
             return cond;
           })
+          ..orderBy([(t) => OrderingTerm.desc(t.receivedAt)])
           ..limit(100))
         .get();