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/core/auth_urls.py

@@ -0,0 +1,15 @@
+from django.urls import path
+
+urlpatterns = []
+
+try:
+    from django.conf import settings
+    if getattr(settings, 'USE_JWT_AUTH', False):
+        from rest_framework_simplejwt.views import TokenObtainPairView, TokenRefreshView
+
+        urlpatterns = [
+            path('auth/token/', TokenObtainPairView.as_view(), name='token_obtain_pair'),
+            path('auth/token/refresh/', TokenRefreshView.as_view(), name='token_refresh'),
+        ]
+except ImportError:
+    pass