feat(documents): wire archiveBox + archiveFolder through DTO and service update

backend/src/main/java/org/raddatz/familienarchiv/dto/DocumentUpdateDTO.java

@@ -13,6 +13,8 @@ public class DocumentUpdateDTO {
     private LocalDate documentDate;
     private String location;
     private String documentLocation;
+    private String archiveBox;
+    private String archiveFolder;
     private String transcription;
     private String summary;
     private UUID senderId;

backend/src/main/java/org/raddatz/familienarchiv/service/DocumentService.java

@@ -271,6 +271,8 @@ public class DocumentService {
         doc.setTranscription(dto.getTranscription());
         doc.setSummary(dto.getSummary());
         doc.setDocumentLocation(dto.getDocumentLocation());
+        doc.setArchiveBox(dto.getArchiveBox());
+        doc.setArchiveFolder(dto.getArchiveFolder());
 
         List<String> tags = new ArrayList<>();
         if (dto.getTags() != null && !dto.getTags().isBlank()) {

backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceTest.java

@@ -121,6 +121,23 @@ class DocumentServiceTest {
                 .isInstanceOf(DomainException.class);
     }
 
+    @Test
+    void updateDocument_setsArchiveBoxAndFolder() throws Exception {
+        UUID id = UUID.randomUUID();
+        Document doc = Document.builder().id(id).receivers(new HashSet<>()).tags(new HashSet<>()).build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenReturn(doc);
+
+        DocumentUpdateDTO dto = new DocumentUpdateDTO();
+        dto.setArchiveBox("K-03");
+        dto.setArchiveFolder("Mappe B");
+
+        documentService.updateDocument(id, dto, null, null);
+
+        assertThat(doc.getArchiveBox()).isEqualTo("K-03");
+        assertThat(doc.getArchiveFolder()).isEqualTo("Mappe B");
+    }
+
     // ─── deleteTagCascading ───────────────────────────────────────────────────
 
     @Test