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

boneyard.config.json

@@ -0,0 +1,7 @@
+{
+  "breakpoints": [375, 768, 1280],
+  "out": "./bones",
+  "wait": 800,
+  "color": "rgba(0,0,0,0.08)",
+  "animate": "pulse"
+}