Fix monitor.js missing from Docker image and SQLITE_CANTOPEN errors

- Copy monitor.js into the standalone build stage (was missing entirely)
- Remove node-fetch require — Node 18 has global fetch built-in
- Switch from bind mount (./data) to named volume (dashboard-data) so
  Docker manages permissions correctly for the nextjs user

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -11,5 +11,8 @@ services:
       - NODE_ENV=production
       - DB_PATH=/app/data/dashboard.db
     volumes:
-      - ./data:/app/data
+      - dashboard-data:/app/data
       - /server_storage:/server_storage:ro
+
+volumes:
+  dashboard-data: