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);