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/test/java/org/raddatz/familienarchiv/person/PersonRepositoryTest.java

@@ -428,6 +428,31 @@ class PersonRepositoryTest {
         assertThat(results).hasSize(1);
     }
 
+    @Test
+    void searchByName_findsByAliasFirstName() {
+        Person clara = personRepository.save(Person.builder().firstName("Clara").lastName("Cram").build());
+        aliasRepository.save(PersonNameAlias.builder()
+                .person(clara).firstName("Wilhelmina").lastName("de Gruyter")
+                .type(PersonNameAliasType.BIRTH).sortOrder(0).build());
+
+        List<Person> results = personRepository.searchByName("Wilhelmina");
+
+        assertThat(results).hasSize(1);
+        assertThat(results.get(0).getLastName()).isEqualTo("Cram");
+    }
+
+    @Test
+    void searchByName_ordersByLastNameThenFirstName() {
+        personRepository.save(Person.builder().firstName("Clara").lastName("Cram").build());
+        personRepository.save(Person.builder().firstName("Anna").lastName("Cram").build());
+        personRepository.save(Person.builder().firstName("Bernd").lastName("Cram").build());
+
+        List<Person> results = personRepository.searchByName("Cram");
+
+        assertThat(results).extracting(Person::getFirstName)
+                .containsExactly("Anna", "Bernd", "Clara");
+    }
+
     // ─── searchWithDocumentCount with aliases ────────────────────────────────
 
     @Test