Add GitHub Pages deployment workflow for website

Publishes website/ via GitHub Actions on every push to main that
touches it, and configures the custom domain satsprice.app.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AejmWBrdE3DbJWbXoaE3aX

.github/workflows/pages.yml

@@ -0,0 +1,37 @@
+name: Deploy website to GitHub Pages
+
+on:
+  push:
+    branches: ["main"]
+    paths:
+      - "website/**"
+      - ".github/workflows/pages.yml"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: "./website"
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4