feat(document): remove conversation repository queries

Delete findConversation and findSinglePersonCorrespondence (no remaining
callers after the service methods were removed) and their integration
test section. Drops the now-unused LocalDate import.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/document/DocumentRepository.java

@@ -15,7 +15,6 @@ import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
-import java.time.LocalDate;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -81,32 +80,6 @@ public interface DocumentRepository extends JpaRepository<Document, UUID>, JpaSp
 
     Optional<Document> findFirstByMetadataCompleteFalseAndIdNot(UUID id, Sort sort);
 
-    @EntityGraph("Document.full")
-    @Query("SELECT DISTINCT d FROM Document d " +
-            "JOIN d.receivers r " +
-            "WHERE " +
-            "((d.sender.id = :person1 AND r.id = :person2) " +
-            " OR " +
-            " (d.sender.id = :person2 AND r.id = :person1)) " +
-            "AND d.documentDate BETWEEN :from AND :to")
-    List<Document> findConversation(
-            @Param("person1") UUID person1,
-            @Param("person2") UUID person2,
-            @Param("from") LocalDate from,
-            @Param("to") LocalDate to,
-            Sort sort);
-
-    @EntityGraph("Document.full")
-    @Query("SELECT DISTINCT d FROM Document d " +
-            "LEFT JOIN d.receivers r " +
-            "WHERE (d.sender.id = :personId OR r.id = :personId) " +
-            "AND d.documentDate BETWEEN :from AND :to")
-    List<Document> findSinglePersonCorrespondence(
-            @Param("personId") UUID personId,
-            @Param("from") LocalDate from,
-            @Param("to") LocalDate to,
-            Sort sort);
-
     @Query(nativeQuery = true, value = """
             SELECT d.id FROM documents d
             CROSS JOIN LATERAL (

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

@@ -262,67 +262,6 @@ class DocumentRepositoryTest {
         assertThat(result.getContent()).allMatch(d -> !d.isMetadataComplete());
     }
 
-    // ─── findSinglePersonCorrespondence — DISTINCT / multi-receiver safety ────
-
-    @Test
-    void findSinglePersonCorrespondence_returnsExactlyOneResult_whenDocumentHasThreeReceiversAndOneMatchesPersonId() {
-        Person sender = personRepository.save(Person.builder()
-                .firstName("Hans").lastName("Müller").build());
-        Person receiver1 = personRepository.save(Person.builder()
-                .firstName("Anna").lastName("Schmidt").build());
-        Person receiver2 = personRepository.save(Person.builder()
-                .firstName("Bertha").lastName("Wagner").build());
-        Person receiver3 = personRepository.save(Person.builder()
-                .firstName("Clara").lastName("Koch").build());
-
-        // Document addressed to all three receivers
-        Document doc = documentRepository.save(Document.builder()
-                .title("Rundschreiben")
-                .originalFilename("rundschreiben.pdf")
-                .status(DocumentStatus.UPLOADED)
-                .sender(sender)
-                .receivers(new HashSet<>(Set.of(receiver1, receiver2, receiver3)))
-                .documentDate(LocalDate.of(1950, 6, 1))
-                .build());
-
-        Sort sort = Sort.by(Sort.Direction.DESC, "documentDate");
-        LocalDate from = LocalDate.of(1900, 1, 1);
-        LocalDate to = LocalDate.of(2000, 1, 1);
-
-        // Query for receiver1 — the DISTINCT must collapse the 3 JOIN rows into 1 result
-        List<Document> results = documentRepository.findSinglePersonCorrespondence(
-                receiver1.getId(), from, to, sort);
-
-        assertThat(results).hasSize(1);
-        assertThat(results.get(0).getId()).isEqualTo(doc.getId());
-    }
-
-    @Test
-    void findSinglePersonCorrespondence_includesDocumentsWherePerson_isSender() {
-        Person sender = personRepository.save(Person.builder()
-                .firstName("Hans").lastName("Müller").build());
-        Person receiver = personRepository.save(Person.builder()
-                .firstName("Anna").lastName("Schmidt").build());
-
-        documentRepository.save(Document.builder()
-                .title("Brief als Absender")
-                .originalFilename("brief_absender.pdf")
-                .status(DocumentStatus.UPLOADED)
-                .sender(sender)
-                .receivers(new HashSet<>(Set.of(receiver)))
-                .documentDate(LocalDate.of(1950, 6, 1))
-                .build());
-
-        Sort sort = Sort.by(Sort.Direction.DESC, "documentDate");
-        LocalDate from = LocalDate.of(1900, 1, 1);
-        LocalDate to = LocalDate.of(2000, 1, 1);
-
-        List<Document> results = documentRepository.findSinglePersonCorrespondence(
-                sender.getId(), from, to, sort);
-
-        assertThat(results).hasSize(1);
-    }
-
     // ─── findSegmentationQueue ────────────────────────────────────────────────
 
     @Test