Deploy: add nginx, systemd services, scripts, MCP info endpoint ...

- nginx reverse proxy on port 80 for UI + /api/ + /mcp/
- systemd user services: backend (8000), MCP SSE (8001)
- install.sh and deploy.sh for automated setup
- /mcp/info endpoint to expose MCP instructions and tools list
- MCP server instructions expanded for AI agent workflows
- Update server README with deployment docs

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Add Gnexus Book MCP server

Add inventory relationship graph API

Add documentation foundation and backend maintenance API