test(search): DataJpaTest for descendant-expansion via TagRepository

Verifies the recursive CTE in findDescendantIdsByName expands a parent tag
to include all child IDs, and that findByNameContainingIgnoreCase matches
both parent and child names when the fragment appears in both.

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

backend/src/test/java/org/raddatz/familienarchiv/search/NlSearchTagResolutionIntegrationTest.java

@@ -0,0 +1,56 @@
+package org.raddatz.familienarchiv.search;
+
+import org.junit.jupiter.api.Test;
+import org.raddatz.familienarchiv.PostgresContainerConfig;
+import org.raddatz.familienarchiv.config.FlywayConfig;
+import org.raddatz.familienarchiv.tag.Tag;
+import org.raddatz.familienarchiv.tag.TagRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.jdbc.test.autoconfigure.AutoConfigureTestDatabase;
+import org.springframework.boot.data.jpa.test.autoconfigure.DataJpaTest;
+import org.springframework.context.annotation.Import;
+
+import java.util.List;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DataJpaTest
+@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
+@Import({PostgresContainerConfig.class, FlywayConfig.class})
+class NlSearchTagResolutionIntegrationTest {
+
+    @Autowired
+    private TagRepository tagRepository;
+
+    @Test
+    void findDescendantIdsByName_parentName_includesChildId() {
+        Tag parent = tagRepository.save(Tag.builder().name("Krieg").build());
+        Tag child = tagRepository.save(Tag.builder().name("Weltkrieg").parentId(parent.getId()).build());
+
+        List<UUID> ids = tagRepository.findDescendantIdsByName("Krieg");
+
+        assertThat(ids).containsExactlyInAnyOrder(parent.getId(), child.getId());
+    }
+
+    @Test
+    void findDescendantIdsByName_childName_returnsOnlyChild() {
+        Tag parent = tagRepository.save(Tag.builder().name("Krieg").build());
+        Tag child = tagRepository.save(Tag.builder().name("Weltkrieg").parentId(parent.getId()).build());
+
+        List<UUID> ids = tagRepository.findDescendantIdsByName("Weltkrieg");
+
+        assertThat(ids).containsExactly(child.getId());
+        assertThat(ids).doesNotContain(parent.getId());
+    }
+
+    @Test
+    void findByNameContainingIgnoreCase_parentSubstring_matchesParentOnly() {
+        Tag parent = tagRepository.save(Tag.builder().name("Krieg").build());
+        tagRepository.save(Tag.builder().name("Weltkrieg").parentId(parent.getId()).build());
+
+        List<Tag> found = tagRepository.findByNameContainingIgnoreCase("Krieg");
+
+        assertThat(found).extracting(Tag::getName).containsExactlyInAnyOrder("Krieg", "Weltkrieg");
+    }
+}