feat: add placeholder index.html pages for 10 module directories
Add HoloLake/AGE OS themed placeholder pages with consistent dark theme
design (#0a0a0f background, #00d4ff accent) for modules under development:
- m10-cloud (云服务), m15-cloud-drive (云盘), m01-login (登录)
- m18-health-check (健康检查), coldstart (冷启动), portal (门户)
- notification (通知), help-center (帮助中心), frontend (前端)
- app (光湖集成壳)
Each page shows module icon, name, development status, contextual
description, back-to-home link, and HoloLake footer branding.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>