feat: improve book reviews, restore detailed privacy policy, fix header logo, add theme toggle, integrate boneyard-js

- Book reviews: add line-clamp for longer review text with expand/collapse per review
- Privacy policy: restore full detailed DSGVO-compliant fallback content
- Header (legal pages): change logo from 'dk' to 'dk0' in circle
- Header (main page): add ThemeToggle for dark/light mode switching
- Skeleton loading: integrate boneyard-js for ReadBooks, CurrentlyReading, Projects
- Add boneyard.config.json and bones/registry.ts placeholder

package.json

@@ -64,6 +64,7 @@
     "@tiptap/react": "^3.15.3",
     "@tiptap/starter-kit": "^3.15.3",
     "@vercel/og": "^0.6.5",
+    "boneyard-js": "^1.7.6",
     "clsx": "^2.1.1",
     "dotenv": "^16.6.1",
     "framer-motion": "^12.24.10",