feat(person): match alias first names in searchByName (#763)

The direct-match classifier accepts alias firstName tokens, so the fetch must
surface candidates matchable only via an alias first name. Add a.firstName to
the searchByName LIKE clause (reuses the bound :query — injection-proof). The
person_name_aliases.first_name column already exists; no migration.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/person/PersonRepository.java

@@ -19,7 +19,8 @@ public interface PersonRepository extends JpaRepository<Person, UUID> {
            "LOWER(CONCAT(COALESCE(p.firstName, ''),' ',p.lastName)) LIKE LOWER(CONCAT('%', :query, '%')) OR " +
            "LOWER(CONCAT(p.lastName, ' ', COALESCE(p.firstName, ''))) LIKE LOWER(CONCAT('%', :query, '%')) OR " +
            "LOWER(p.alias) LIKE LOWER(CONCAT('%', :query, '%')) OR " +
-           "LOWER(a.lastName) LIKE LOWER(CONCAT('%', :query, '%')) " +
+           "LOWER(a.lastName) LIKE LOWER(CONCAT('%', :query, '%')) OR " +
+           "LOWER(a.firstName) LIKE LOWER(CONCAT('%', :query, '%')) " +
            "ORDER BY p.lastName ASC, p.firstName ASC")
     List<Person> searchByName(@Param("query") String query);