test(timeline): add integration tests for TimelineService + findByGeneration

Verifies PersonRepository.findByGeneration handles match, no-match (empty
list not NPE), and null-generation persons (excluded). Also confirms
TimelineService.assemble() returns a persisted curated event in the
correct year band against real Postgres via Testcontainers.

Refs #777
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/java/org/raddatz/familienarchiv/timeline/TimelineServiceIntegrationTest.java

@@ -0,0 +1,105 @@
+package org.raddatz.familienarchiv.timeline;
+
+import jakarta.persistence.EntityManager;
+import jakarta.persistence.PersistenceContext;
+import org.junit.jupiter.api.Test;
+import org.raddatz.familienarchiv.PostgresContainerConfig;
+import org.raddatz.familienarchiv.document.DatePrecision;
+import org.raddatz.familienarchiv.person.Person;
+import org.raddatz.familienarchiv.person.PersonRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.bean.override.mockito.MockitoBean;
+import org.springframework.transaction.annotation.Transactional;
+import software.amazon.awssdk.services.s3.S3Client;
+
+import java.time.LocalDate;
+import java.util.List;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link TimelineService} and {@link PersonRepository#findByGeneration}
+ * against real Postgres. Verifies that assembled output reflects persisted curated events and
+ * that the generation query handles null-generation rows correctly.
+ */
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE)
+@ActiveProfiles("test")
+@Import(PostgresContainerConfig.class)
+@Transactional
+class TimelineServiceIntegrationTest {
+
+    @MockitoBean S3Client s3Client;
+
+    @Autowired TimelineService timelineService;
+    @Autowired TimelineEventRepository timelineEventRepository;
+    @Autowired PersonRepository personRepository;
+
+    @PersistenceContext EntityManager em;
+
+    // ─── PersonRepository.findByGeneration ────────────────────────────────────
+
+    @Test
+    void findByGeneration_returns_matching_persons() {
+        personRepository.save(Person.builder().lastName("Gen2A").generation(2).build());
+        personRepository.save(Person.builder().lastName("Gen2B").generation(2).build());
+        personRepository.save(Person.builder().lastName("Gen3").generation(3).build());
+        em.flush();
+
+        List<Person> result = personRepository.findByGeneration(2);
+
+        assertThat(result).extracting(Person::getLastName)
+                .containsExactlyInAnyOrder("Gen2A", "Gen2B");
+    }
+
+    @Test
+    void findByGeneration_returns_empty_list_not_npe_when_no_match() {
+        personRepository.save(Person.builder().lastName("Gen1").generation(1).build());
+        em.flush();
+
+        List<Person> result = personRepository.findByGeneration(99);
+
+        assertThat(result).isNotNull().isEmpty();
+    }
+
+    @Test
+    void findByGeneration_does_not_return_null_generation_persons() {
+        personRepository.save(Person.builder().lastName("NullGen").build()); // generation stays null
+        em.flush();
+
+        List<Person> result = personRepository.findByGeneration(1);
+
+        assertThat(result).extracting(Person::getLastName).doesNotContain("NullGen");
+    }
+
+    // ─── TimelineService.assemble end-to-end ─────────────────────────────────
+
+    @Test
+    void assemble_includes_persisted_curated_event_in_correct_year_band() {
+        UUID actorId = UUID.randomUUID();
+        TimelineEvent event = timelineEventRepository.save(TimelineEvent.builder()
+                .title("Sarajevo")
+                .type(EventType.HISTORICAL)
+                .eventDate(LocalDate.of(1914, 6, 28))
+                .precision(DatePrecision.DAY)
+                .createdBy(actorId)
+                .updatedBy(actorId)
+                .build());
+        em.flush();
+        em.clear();
+
+        TimelineDTO result = timelineService.assemble(new TimelineFilter(null, null, null, null, null));
+
+        assertThat(result.years()).anySatisfy(y -> {
+            assertThat(y.year()).isEqualTo(1914);
+            assertThat(y.entries()).anySatisfy(e -> {
+                assertThat(e.title()).isEqualTo("Sarajevo");
+                assertThat(e.kind()).isEqualTo(Kind.EVENT);
+                assertThat(e.eventId()).isEqualTo(event.getId());
+            });
+        });
+    }
+}