feat: Add book ratings and reviews managed via Directus CMS

Adds a new "Read Books" section below "Currently Reading" in the About
page. Book reviews with star ratings and comments are fetched from a
Directus CMS collection (book_reviews) and displayed with the existing
liquid design system. Includes i18n support (EN/DE), show more/less
toggle, and graceful fallback when the CMS collection does not exist yet.

https://claude.ai/code/session_017E8W9CcHFM5WQVHw74JP34

messages/en.json

@@ -64,6 +64,12 @@
       "currentlyReading": {
         "title": "Currently Reading",
         "progress": "Progress"
+      },
+      "readBooks": {
+        "title": "Read",
+        "finishedAt": "Finished",
+        "showMore": "{count} more",
+        "showLess": "Show less"
       }
     },
     "projects": {