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

docker-compose.yml

@@ -131,6 +131,39 @@ services:
 
     restart: "no"
 
+  # ==========================================================================
+  # Scheduled logical backups of BOTH databases (procurement + casdoor).
+  # Writes pg_dump -Fc archives to a bind mount (default ./backups, point
+  # BACKUP_DIR at /srv/erp/backups on the VPS) and prunes archives older
+  # than BACKUP_KEEP_DAYS. Runs on the same postgres:18 image already pulled.
+  # ==========================================================================
+  db-backup:
+    image: postgres:18
+    container_name: procurement-db-backup
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      PGPASSWORD: ${POSTGRES_PASSWORD:-postgres}
+      BACKUP_INTERVAL_SECONDS: ${BACKUP_INTERVAL_SECONDS:-86400}
+      BACKUP_KEEP_DAYS: ${BACKUP_KEEP_DAYS:-14}
+    volumes:
+      - ${BACKUP_DIR:-./backups}:/backups
+    entrypoint: >
+      /bin/sh -c "
+      echo 'db-backup: dumping every $${BACKUP_INTERVAL_SECONDS}s, keeping $${BACKUP_KEEP_DAYS} days';
+      while true; do
+        STAMP=$$(date +%Y%m%d-%H%M%S);
+        pg_dump -h postgres -U postgres -d procurement -Fc -f /backups/procurement-$${STAMP}.dump &&
+          echo \"db-backup: procurement -> /backups/procurement-$${STAMP}.dump\";
+        pg_dump -h postgres -U postgres -d casdoor -Fc -f /backups/casdoor-$${STAMP}.dump &&
+          echo \"db-backup: casdoor -> /backups/casdoor-$${STAMP}.dump\";
+        find /backups -name '*.dump' -mtime +$${BACKUP_KEEP_DAYS} -delete;
+        sleep $${BACKUP_INTERVAL_SECONDS};
+      done
+      "
+    restart: unless-stopped
+
   # ==========================================================================
   # v2.6 — Casdoor (OIDC identity provider)
   # Console: http://localhost:8080 (admin / 123)