feat(annotations): add createOcrAnnotation that skips overlap check

OCR creates many adjacent text line annotations that would fail the
existing overlap check. createOcrAnnotation() accepts an optional
polygon and bypasses overlap detection entirely.

Refs #227

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

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

@@ -48,6 +48,26 @@ public class AnnotationService {
         return annotationRepository.save(annotation);
     }
 
+    @Transactional
+    public DocumentAnnotation createOcrAnnotation(UUID documentId, CreateAnnotationDTO dto,
+                                                   UUID userId, String fileHash,
+                                                   List<List<Double>> polygon) {
+        DocumentAnnotation annotation = DocumentAnnotation.builder()
+                .documentId(documentId)
+                .pageNumber(dto.getPageNumber())
+                .x(dto.getX())
+                .y(dto.getY())
+                .width(dto.getWidth())
+                .height(dto.getHeight())
+                .color(dto.getColor())
+                .fileHash(fileHash)
+                .createdBy(userId)
+                .polygon(polygon)
+                .build();
+
+        return annotationRepository.save(annotation);
+    }
+
     @Transactional
     public void deleteAnnotation(UUID documentId, UUID annotationId, UUID userId) {
         DocumentAnnotation annotation = annotationRepository