feat: update interests templates for category-based data model

Interests are now grouped by category (matching skills pattern).
Updated cv-interests.njk to iterate categories, cv.js fallback to {},
and cv.njk hasCvData check to include interests.

_data/cv.js

@@ -30,7 +30,7 @@ export default function () {
       skillTypes: {},
       languages: [],
       education: [],
-      interests: [],
+      interests: {},
       interestTypes: {},
     };
   }