add documentation site with markdown rendering (M12)

portal/internal/web/docs/index.md

@@ -0,0 +1,51 @@
+# Mosis Developer Documentation
+
+Welcome to the Mosis developer documentation. Mosis is a virtual smartphone OS for VR games and applications, providing a phone-like device that users can interact with inside VR environments.
+
+## Quick Links
+
+- [Getting Started](getting-started.md) - Create your first Mosis app
+- [UI Guide](guides/ui-design.md) - Design beautiful interfaces with RML/RCSS
+- [Lua Scripting](guides/lua-scripting.md) - Add interactivity with Lua
+- [API Reference](api/lua-api.md) - Complete Lua API documentation
+- [Manifest Reference](api/manifest.md) - App manifest schema
+
+## What is Mosis?
+
+Mosis provides a virtual phone interface for VR applications. Developers can create apps that run inside this virtual phone, offering users familiar smartphone experiences within VR games.
+
+### Key Features
+
+- **RML/RCSS UI** - HTML/CSS-like markup for building interfaces
+- **Lua Scripting** - Lightweight scripting for app logic
+- **Sandboxed Execution** - Secure isolation per app
+- **Cross-Platform** - Works with Unity, Unreal Engine, and more
+
+### Architecture
+
+```
+┌─────────────────────────────────────────┐
+│           Your VR Game/App              │
+│    (Unity, Unreal, native Android)      │
+└──────────────────┬──────────────────────┘
+                   │
+┌──────────────────▼──────────────────────┐
+│            MosisService                 │
+│  ┌─────────────────────────────────┐    │
+│  │     Your Mosis App              │    │
+│  │  ┌─────────┐ ┌─────────────┐    │    │
+│  │  │ RML/CSS │ │ Lua Scripts │    │    │
+│  │  └─────────┘ └─────────────┘    │    │
+│  └─────────────────────────────────┘    │
+└─────────────────────────────────────────┘
+```
+
+## Getting Help
+
+- [Troubleshooting](troubleshooting.md) - Common issues and solutions
+- [FAQ](faq.md) - Frequently asked questions
+- [API Status](https://status.omixlab.com) - Service status page
+
+## Contributing
+
+Mosis is developed by OmixLab LTD. For questions or feedback, contact us through the developer portal.