Audit capture is a process-global; writes made in Celery tasks are never audited #498

Tier 1: correctness

Problem

framework/db/simple_module_db/listeners.py:57,97-98 stores the DatabaseState in a module-level global (global _db_state; _db_state = db_state). The audit hooks read it at lines 214 and 239. Only install_listeners sets it, and only the create_app path calls that.

Celery workers never run create_app. background_tasks/sync_db.py:120-123 calls only attach_session_listeners(WorkerSession), so in a worker _db_state is None and every write a task makes skips audit capture with no signal. The audit_log module installs audit_callback on app.state.sm.db, which a worker doesn't have.

Second problem: the last app built in a process wins the global. That leaks between apps in tests and in any multi-app process.

Smaller layering leak: listeners.py:219 imports simple_module_hosting.logging from the db package, behind a try/except.

Fix

• Attach the audit policy per engine or session, the same way tenancy already does with bind_engine_policy, instead of using a module global.
• Wire the audit callback into the worker bootstrap.
• Add a test: a Celery task (run eagerly) that writes an audited model produces an audit row.