fix(gateway): route local L2 timers to scene extraction

[RerankerGuo]

Description | 描述

Route standalone LocalStateBackend legacy timers consistently with the Redis timer scanner:

• L2_schedule now enqueues a normal L2 task so scene extraction runs.
• L1_idle now enqueues a normal L1 task.
• Explicit offload-l2:* timers continue to use the offload worker and keep targetMmdFile extraction.

The local timer parsing is extracted into a small helper with regression tests.

Related Issue | 关联 Issue

Fix #226

Change Type | 修改类型

• Bug fix | Bug 修复
• New feature | 新功能
• Documentation update | 文档更新
• Code optimization | 代码优化

Self-test Checklist | 自测清单

• Verified locally | 本地验证通过
• No existing features affected | 无影响现有功能

Additional Notes | 其他说明

Verified with Node v24.15.0:

• npm test -- src/gateway/timer-routing.test.ts
• npm test
• npm run build

[Maxwell-Code07]

Thanks for the quick follow-up fix to #226! The timer routing logic is now consistent between standalone and Redis modes. We'll review shortly.