chore: add GitHub Pages deploy workflow and CNAME

Astro build + test + deploy via GitHub Actions.
Custom domain: sshtoolkit.otaviomiranda.com.br

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: luizomf

.github/workflows/deploy.yml

@@ -0,0 +1,44 @@
+name: Deploy to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+
+      - run: npm ci
+      - run: npm test
+      - run: npm run build
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: dist/
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - id: deployment
+        uses: actions/deploy-pages@v4

public/CNAME

@@ -0,0 +1 @@
+sshtoolkit.otaviomiranda.com.br