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>

Dockerfile

@@ -47,6 +47,8 @@ COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
 # Create data directory for SQLite
 RUN mkdir -p /app/data && chown nextjs:nodejs /app/data
 
+# Copy monitor script and startup script
+COPY --from=builder --chown=nextjs:nodejs /app/monitor.js ./
 COPY --chown=nextjs:nodejs start.sh ./
 RUN chmod +x start.sh