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

bones/registry.ts

@@ -0,0 +1,6 @@
+// Boneyard skeleton registry - auto-generated by `npx boneyard-js build`
+// This file is imported once at app initialization to register all bone layouts.
+// Run `npx boneyard-js build` to generate bone files from your components.
+const registry: Record<string, unknown> = {};
+
+export default registry;