Initial documentation structure

ARCHITECTURE.md

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+# APEX OS Architecture
+
+Last Updated: 2026-07-02
+
+## Overview
+APEX OS is a self-hosted AI operating system running on Docker.
+
+## Components
+- **Infrastructure**: Docker, Traefik, PostgreSQL, Redis
+- **AI Platform**: LiteLLM, Ollama, OpenRouter, Open WebUI
+- **Development**: Gitea, Code-Server, n8n, Dockge
+- **Monitoring**: Grafana, Prometheus, Loki
+- **Security**: Vaultwarden, Docker Socket Proxy
+
+## Network
+All services on apex_apex-net bridge network.
+Public access via Traefik reverse proxy with Let's Encrypt SSL.
+
+## Data Flow
+```
+User -> Traefik (SSL/Routing) -> Service Container -> PostgreSQL/Redis
+```
+
+## Service Dependencies
+- All services depend on Docker and Traefik
+- AI services depend on LiteLLM as gateway
+- Monitoring depends on Prometheus for metrics collection