test(transcription): JOIN FETCH query loads all block mentions for propagation

Add findByPersonIdWithMentionsFetched to TranscriptionBlockRepository: subquery
finds blocks referencing the renamed person, outer JOIN FETCH loads their full
mentionedPersons collection. Avoids N+1 lazy selects in the propagation listener.
Filtered JOIN FETCH (WHERE m.personId=:personId) was rejected — it loads only one
mention entry per block, risking data loss on saveAllAndFlush.

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

backend/src/main/java/org/raddatz/familienarchiv/repository/TranscriptionBlockRepository.java

@@ -31,6 +31,15 @@ public interface TranscriptionBlockRepository extends JpaRepository<Transcriptio
 
     List<TranscriptionBlock> findByMentionedPersons_PersonId(UUID personId);
 
+    @Query("""
+            SELECT DISTINCT b FROM TranscriptionBlock b
+            JOIN FETCH b.mentionedPersons
+            WHERE b.id IN (
+                SELECT bb.id FROM TranscriptionBlock bb JOIN bb.mentionedPersons m WHERE m.personId = :personId
+            )
+            """)
+    List<TranscriptionBlock> findByPersonIdWithMentionsFetched(@Param("personId") UUID personId);
+
     void deleteByAnnotationId(UUID annotationId);
 
     int countByDocumentId(UUID documentId);

backend/src/test/java/org/raddatz/familienarchiv/repository/TranscriptionBlockMentionsRepositoryTest.java

@@ -92,4 +92,36 @@ class TranscriptionBlockMentionsRepositoryTest {
         TranscriptionBlock reloaded = blockRepository.findById(saved.getId()).orElseThrow();
         assertThat(reloaded.getMentionedPersons()).isEmpty();
     }
+
+    @Test
+    void findByPersonIdWithMentionsFetched_returnsOnlyBlocksReferencingPerson_withMentionsLoaded() {
+        UUID augusteId = UUID.randomUUID();
+        UUID hermannId = UUID.randomUUID();
+
+        blockRepository.saveAndFlush(TranscriptionBlock.builder()
+                .annotationId(annotationId).documentId(documentId)
+                .text("Brief von @Auguste Raddatz an @Hermann Müller.")
+                .sortOrder(0)
+                .mentionedPersons(List.of(
+                        new PersonMention(augusteId, "Auguste Raddatz"),
+                        new PersonMention(hermannId, "Hermann Müller")))
+                .build());
+        blockRepository.saveAndFlush(TranscriptionBlock.builder()
+                .annotationId(annotationId).documentId(documentId)
+                .text("Unrelated block without Auguste.")
+                .sortOrder(1)
+                .mentionedPersons(List.of(new PersonMention(hermannId, "Hermann Müller")))
+                .build());
+        em.clear();
+
+        List<TranscriptionBlock> result =
+                blockRepository.findByPersonIdWithMentionsFetched(augusteId);
+
+        assertThat(result).hasSize(1);
+        assertThat(result.get(0).getMentionedPersons())
+                .extracting(PersonMention::getPersonId, PersonMention::getDisplayName)
+                .containsExactlyInAnyOrder(
+                        org.assertj.core.groups.Tuple.tuple(augusteId, "Auguste Raddatz"),
+                        org.assertj.core.groups.Tuple.tuple(hermannId, "Hermann Müller"));
+    }
 }