Constant AUDIT_TABLE_DDL 

pub const AUDIT_TABLE_DDL: &str = r#"
CREATE TABLE IF NOT EXISTS cratestack_audit (
    event_id UUID PRIMARY KEY,
    schema_name TEXT NOT NULL,
    model TEXT NOT NULL,
    operation TEXT NOT NULL,
    primary_key JSONB NOT NULL,
    actor JSONB NOT NULL,
    tenant TEXT,
    before JSONB,
    after JSONB,
    request_id TEXT,
    occurred_at TIMESTAMPTZ NOT NULL,
    delivered_at TIMESTAMPTZ,
    attempts BIGINT NOT NULL DEFAULT 0,
    last_error TEXT
);

CREATE INDEX IF NOT EXISTS cratestack_audit_model_idx
    ON cratestack_audit (schema_name, model, occurred_at DESC);

CREATE INDEX IF NOT EXISTS cratestack_audit_tenant_idx
    ON cratestack_audit (tenant, occurred_at DESC)
    WHERE tenant IS NOT NULL;

CREATE INDEX IF NOT EXISTS cratestack_audit_undelivered_idx
    ON cratestack_audit (occurred_at)
    WHERE delivered_at IS NULL;
"#;

DDL for the audit log table. Banks typically run migrations through their own tooling — this DDL is exposed so the crate::SqlxRuntime can idempotently ensure the table exists during bootstrap.