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 500ed - the import's 'importer' account being the
guaranteed case (its PAT plus every audit row the import wrote).
Tokens are revoked outright; audit history is kept but detached
(userid NULL), 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