Run a subscription and payment audit against Stripe

Admin-only. Runs one read-only audit that compares every Stripe subscription, invoice, charge, refund, and dispute with local entitlements, invoice snapshots, period ledgers, and frozen statements, records the run, and returns it with findings, evidence, and repair paths. Optional user_id scopes the run to one customer; scoped runs are recorded but do not affect the scheduled run's diff or emails. Never changes Stripe or local billing data.