test(document): add query-count assertion for findAll(Pageable) path

Adds failing test: findAll(Pageable) must not N+1 sender for 5 docs.
Without @EntityGraph override for this overload, each document triggers
a separate SELECT for its lazy sender.

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

backend/src/test/java/org/raddatz/familienarchiv/document/DocumentRepositoryTest.java

@@ -560,6 +560,31 @@ class DocumentRepositoryTest {
                 .isLessThanOrEqualTo(2);
     }
 
+    @Test
+    void findAll_withPageable_loadsSenderWithoutNPlusOne() {
+        Person sender = personRepository.save(Person.builder().firstName("Maria").lastName("RaSender").build());
+        Tag tag = tagRepository.save(Tag.builder().name("RaTag2").build());
+        for (int i = 0; i < 5; i++) {
+            documentRepository.save(Document.builder()
+                    .title("RaDoc2 " + i).originalFilename("radoc2_" + i + ".pdf")
+                    .status(DocumentStatus.UPLOADED)
+                    .sender(sender)
+                    .tags(new HashSet<>(Set.of(tag)))
+                    .build());
+        }
+        entityManager.flush();
+        entityManager.clear();
+        Statistics stats = entityManagerFactory.unwrap(SessionFactory.class).getStatistics();
+        stats.setStatisticsEnabled(true);
+        stats.clear();
+
+        documentRepository.findAll(PageRequest.of(0, 5, Sort.by(Sort.Direction.DESC, "updatedAt")));
+
+        assertThat(stats.getPrepareStatementCount())
+                .as("@EntityGraph(Document.list) via findAll(Pageable) must not N+1 sender for 5 docs")
+                .isLessThanOrEqualTo(5);
+    }
+
     // ─── seeding helpers ─────────────────────────────────────────────────────
 
     private Document uploaded(String title) {