feat(data-safety): scheduled DB backups + audit trail + verified actor attribution

- db-backup sidecar: pg_dump -Fc of procurement+casdoor every
  BACKUP_INTERVAL_SECONDS into BACKUP_DIR, retention via BACKUP_KEEP_DAYS
- audit_log table (migration.sql + runtime ensure_audit_table) with
  model + transactional helper (utils/audit.record) — wired into user
  create/role-change and inventory transaction creation
- get_actor: quote_events.actor now stores the VERIFIED user's display
  name instead of the raw bearer token

sql/migration.sql

@@ -634,4 +634,15 @@ CREATE TRIGGER trg_item_decisions_sync_price
 -- double-applied. Arrival auto-posting (POST /pm/receipts) goes through
 -- the same service path and is idempotent via receipt_allocation_id.
 
+-- ---------- AUDIT LOG (general activity trail, v2.7) ----------
+CREATE TABLE IF NOT EXISTS audit_log (
+    id          UUID        NOT NULL DEFAULT gen_random_uuid() PRIMARY KEY,
+    occurred_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    actor       TEXT,
+    action      TEXT        NOT NULL,
+    entity      TEXT        NOT NULL,
+    entity_id   TEXT,
+    details     JSONB       NOT NULL DEFAULT '{}'
+);
+
 COMMIT;