Enable KeyStatic CMS for production

Changes:
- Added Netlify adapter for server-side rendering
- Changed output mode from static to server
- Updated KeyStatic storage from local to GitHub
- Removed SKIP_KEYSTATIC from Netlify build
- KeyStatic Admin UI will be available at /keystatic

Features:
- Server-side rendering with Netlify Functions
- GitHub integration for content management
- Production-ready KeyStatic Admin UI

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

package.json

@@ -22,6 +22,7 @@
   },
   "dependencies": {
     "@astrojs/markdoc": "^0.15.10",
+    "@astrojs/netlify": "^6.6.4",
     "@astrojs/react": "^4.4.2",
     "@astrojs/rss": "^4.0.11",
     "@astrojs/sitemap": "^3.3.0",
@@ -32,6 +33,7 @@
     "@keystatic/core": "^0.5.48",
     "@types/react": "^19.2.8",
     "@types/react-dom": "^19.2.3",
+    "ajv": "^8.17.1",
     "astro": "^5.7.3",
     "astro-embed": "^0.9.0",
     "astro-icon": "^1.1.5",