**docs:** expand index.md with architecture, quick start, and tech stack

- Add detailed architecture and workflow diagram to explain dashboard functionality
- Include a "Quick Start" section with Docker Compose setup instructions
- Document tech stack and layers used in the project
- Enhance feature descriptions for better clarity and user guidance

docs/index.md

@@ -19,4 +19,70 @@ features:
     details: Events are stored in SQLite so they survive restarts. No external database required.
   - title: Organize with Tags
     details: Group and tag images to keep your update notifications organized. Dismiss updates you've reviewed.
+  - title: Secure by Default
+    details: Optional token-based webhook authentication. Just set WEBHOOK_SECRET and you're protected.
+  - title: Docker Ready
+    details: Ship with a multi-stage Dockerfile and Docker Compose configs for both production and development.
+  - title: REST API
+    details: Full JSON API for updates, tags, assignments, and acknowledgements. Easy to integrate with other tools.
 ---
+
+## Quick Start
+
+Get up and running in seconds with Docker Compose:
+
+```yaml
+# compose.yml
+services:
+  diun-dashboard:
+    image: gitea.jeanlucmakiola.de/makiolaj/diundashboard:latest
+    ports:
+      - "8080:8080"
+    environment:
+      - DB_PATH=/data/diun.db
+      - WEBHOOK_SECRET=your-secret-here  # optional
+    volumes:
+      - diun-data:/data
+
+volumes:
+  diun-data:
+```
+
+```bash
+docker compose up -d
+# open http://localhost:8080
+```
+
+## How It Works
+
+<div class="architecture">
+
+**DIUN** detects Docker image updates and sends a webhook to the dashboard. The Go backend persists events to SQLite and serves them via a REST API. The React frontend polls for updates and displays them in a modern, responsive UI.
+
+</div>
+
+```
+┌───────┐    POST /webhook    ┌──────────────┐    SQLite    ┌─────────┐
+│  DIUN │ ──────────────────► │  Go Backend  │ ◄──────────► │ diun.db │
+└───────┘                     └──────┬───────┘              └─────────┘
+                                     │
+                              GET /api/updates
+                                     │
+                              ┌──────▼───────┐
+                              │  React SPA   │
+                              │  (Dashboard) │
+                              └──────────────┘
+```
+
+### Tech Stack
+
+| Layer | Technology |
+|-------|-----------|
+| Backend | Go, `net/http`, `modernc.org/sqlite` |
+| Frontend | React 19, Vite, Tailwind CSS, shadcn/ui |
+| Database | SQLite (embedded, no external deps) |
+| Tooling | Bun, Docker, Gitea Actions CI/CD |
+
+## Screenshot
+
+> *Screenshot coming soon — run the dashboard locally to see it in action!*