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/views.py

@@ -0,0 +1,30 @@
+from rest_framework.decorators import api_view
+from rest_framework.response import Response
+
+from .choices import (
+    RELATION_TYPES,
+    LIFE_SPHERES,
+    NETWORK_CIRCLES,
+    INTERACTION_INTENSITY,
+    choices_payload,
+)
+
+
+@api_view(['GET'])
+def meta_choices(request):
+    """Unified meta endpoint for all domain enums."""
+    return Response(choices_payload())
+
+
+@api_view(['GET'])
+def relation_types(request):
+    return Response([{'value': v, 'label': l} for v, l in RELATION_TYPES])
+
+
+@api_view(['GET'])
+def network_map_choices(request):
+    return Response({
+        'life_spheres': [{'value': v, 'label': l} for v, l in LIFE_SPHERES],
+        'network_circles': [{'value': v, 'label': l} for v, l in NETWORK_CIRCLES],
+        'interaction_intensities': [{'value': v, 'label': l} for v, l in INTERACTION_INTENSITY],
+    })