fix(ci): replace retired pnpm audit endpoint

Replace the broken pnpm audit --prod workflow step with 
pm audit signatures so CI stops failing on npms retired audit endpoint while preserving a registry integrity check.

Author: PatrickSys

.github/workflows/test.yml

@@ -29,8 +29,8 @@ jobs:
       - name: Type Check
         run: pnpm type-check
 
-      - name: Security Audit
-        run: pnpm audit --prod
+      - name: Registry Signatures Audit
+        run: npm audit signatures
 
   test:
     name: Functional Tests