refactor(front): extract shared utils and rewire pages

app/shared/apiRelations.ts

@@ -23,7 +23,7 @@ export const extractRelationId = (value: unknown): string | null => {
     }
     if (trimmed.includes('/')) {
       const parts = trimmed.split('/').filter(Boolean);
-      return parts.length ? parts[parts.length - 1] : null;
+      return parts.length ? (parts[parts.length - 1] ?? null) : null;
     }
     return trimmed;
   }