docs: Starlight documentation site (#24)

* docs: replace MkDocs with Starlight documentation site

- Astro/Starlight for modern static site generation
- Complete documentation covering:
  - Getting started (intro, install, config, first deployment)
  - Stack details (Dockerfile, Nginx, PHP, Supervisor)
  - Architecture (Coolify, Postgres+Dragonfly, Horizon, Reverb)
  - All artisan commands
  - Dashboard and API reference
  - Advanced topics (customization, multi-app, CI/CD)
- GitHub Actions workflow for Pages deployment
- Mermaid diagrams for architecture visualization

Closes #21

Stu Mason + AI <me@stumason.dev>

* docs: add simple index page

Stu Mason + AI <me@stumason.dev>

* docs: add mermaid support and improve stack overview

- Add starlight-client-mermaid plugin for diagram rendering
- Rewrite stack overview to clearly show Coolify resources
- Show Project > Environment > App/DB/Cache hierarchy
- Clarify Dockerfile + private key deployment model

Stu Mason + AI <me@stumason.dev>

* docs: replace boilerplate README with project docs

Stu Mason + AI <me@stumason.dev>

Author: StuMason

.github/workflows/deploy-docs.yml

@@ -0,0 +1,60 @@
+name: Deploy Docs
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'docs/**'
+      - '.github/workflows/deploy-docs.yml'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+          cache-dependency-path: docs/package-lock.json
+
+      - name: Setup Pages
+        id: pages
+        uses: actions/configure-pages@v4
+
+      - name: Install dependencies
+        working-directory: docs
+        run: npm ci
+
+      - name: Build
+        working-directory: docs
+        run: npm run build
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: docs/dist
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

docs/.gitignore

@@ -0,0 +1,21 @@
+# build output
+dist/
+# generated types
+.astro/
+
+# dependencies
+node_modules/
+
+# logs
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+
+
+# environment variables
+.env
+.env.production
+
+# macOS-specific files
+.DS_Store