Users: deleting a user clears their API tokens and detaches audit rows

Deleting any user who owned an API token or appeared in the audit log
hit the users FK and returned 500. Tokens are revoked outright; audit
history is kept but detached so the trail survives the account.

tests/test_core/test_users_api.py

@@ -0,0 +1,29 @@
+
+
+def test_delete_user_with_tokens_and_audit_history(client, auth_headers, app, db):
+    """Deleting a user revokes their API tokens and detaches (not deletes)
+    their audit rows - the importer-user case."""
+    from werkzeug.security import generate_password_hash
+    from shopdb.core.models import User, ApiToken, AuditLog
+
+    with app.app_context():
+        user = User(username='importer2', email='importer2@test.local',
+                    passwordhash=generate_password_hash('x'), isactive=True)
+        db.session.add(user)
+        db.session.flush()
+        db.session.add(ApiToken(userid=user.userid, name='import token',
+                                tokenprefix='deadbeef', tokenhash='x' * 64))
+        db.session.add(AuditLog(userid=user.userid, action='created',
+                                entitytype='Asset', entityid=1,
+                                entityname='imported thing'))
+        db.session.commit()
+        userid = user.userid
+
+    response = client.delete(f'/api/users/{userid}', headers=auth_headers)
+    assert response.status_code == 200, response.get_json()
+
+    with app.app_context():
+        assert db.session.get(User, userid) is None
+        assert ApiToken.query.filter_by(userid=userid).count() == 0
+        detached = AuditLog.query.filter_by(entityname='imported thing').one()
+        assert detached.userid is None