Add plugin platform with modular backend and frontend registry.

Split graph/import/meta into Django apps, add API v1 with OpenAPI and pytest, and introduce plugin registry with the tags reference plugin on both FE and BE.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/import_export/views.py

@@ -0,0 +1,19 @@
+from rest_framework import status
+from rest_framework.decorators import api_view
+from rest_framework.response import Response
+
+from .services import parse_upload_file, import_contacts_from_rows
+
+
+@api_view(['POST'])
+def import_contacts(request):
+    file = request.FILES.get('file')
+    if not file:
+        return Response({'error': 'Файл не передан.'}, status=status.HTTP_400_BAD_REQUEST)
+    try:
+        rows, error = parse_upload_file(file)
+        if error:
+            return Response({'error': error}, status=status.HTTP_400_BAD_REQUEST)
+        return Response(import_contacts_from_rows(rows))
+    except Exception as e:
+        return Response({'error': f'Ошибка разбора файла: {e}'}, status=status.HTTP_400_BAD_REQUEST)