feat(rn): [P1] Runtime settings

[liuyidi]

Summary

Runtime/system settings: bot name, timezone, paths; gateway restart optional on mobile.

WebUI reference

• webui/src/pages/settings/runtime/RuntimeSettings.tsx
• webui/src/pages/settings/runtime/useRuntimeSettings.ts

API

• POST /api/settings/update (bot name / timezone, etc.)

RN landing

• New: src/app/settings/runtime.tsx + Me entry

Acceptance

• Edit bot name / timezone and save
• Restart gateway marked desktop-first / optional on mobile

Depends

• chore: Settings API thin wrapper