feat: add marketing landing page for crumbs.bretzel.app

Static landing page with parchment/retro theme matching the app aesthetic.
Includes GitHub Pages deploy workflow, responsive layout, feature grid,
deploy quick-start, and 404 page. Screenshot placeholders ready for
real captures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/website.yml

@@ -0,0 +1,36 @@
+name: Deploy Website
+
+on:
+  push:
+    branches: [main]
+    paths: ['website/**']
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    name: Deploy to GitHub Pages
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/configure-pages@v5
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: website
+
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4