ci: set dummy Clerk key for Next build in CI

.github/workflows/ci.yml

@@ -47,4 +47,10 @@ jobs:
         run: make setup
 
       - name: Run checks
+        env:
+          # Keep CI builds deterministic and secretless.
+          NEXT_TELEMETRY_DISABLED: "1"
+          # Clerk is required at Next build/prerender time in this repo.
+          # Use a dummy publishable key so forks/PRs can still validate.
+          NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY: "pk_test_00000000000000000000000000000000"
         run: make check