Add JWT auth with per-user data isolation and account settings.

Users can register, log in, and manage profile/password in a personal account page; server data is scoped by owner across contacts, maps, tags, and import.

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

backend/tests/test_graph_api.py

@@ -9,7 +9,7 @@ def test_graph_empty(api_client):
 
 
 @pytest.mark.django_db
-def test_graph_with_data(api_client, sample_contact, sample_relation):
+def test_graph_with_data(api_client, sample_relation):
     response = api_client.get('/api/v1/graph/')
     assert response.status_code == 200
     assert len(response.data['nodes']) == 2