docs: reorganize documentation with i18n and Swagger API reference

- Add per-submodule docs structure (server-core, dashboard-ui, device-agent)
- Restructure VitePress with i18n support (Indonesian default + English)
- Add Swagger API reference pages with Swagger UI CDN embed
- Create merge.js script for combining sidebar manifests
- Integrate docs build into Docker (update.sh + nginx volume mount)
- Add documentation section to root README

README.md

@@ -221,6 +221,41 @@ For automated client deployment with the Device Agent:
 
 ---
 
+## 📚 Documentation
+
+Documentation is built with VitePress and served at `/docs/`.
+
+### Local Development
+
+```bash
+cd apps/docs
+npm install
+npm run docs:dev
+```
+
+### Building Docs
+
+```bash
+cd apps/docs
+npm run docs:build
+```
+
+The output is in `apps/docs/.vitepress/dist/`.
+
+### Structure
+
+- `apps/docs/` — VitePress root (i18n: Indonesian + English)
+- `apps/server-core/docs/` — Backend API docs & guides
+- `apps/dashboard-ui/docs/` — Dashboard UI docs
+- `apps/device-agent/docs/` — Device Agent docs
+
+### Languages
+
+- **Bahasa Indonesia** (default): `/docs/`
+- **English**: `/docs/en/`
+
+---
+
 ## 📁 File Structure
 
 ```