test(frontend): add Vitest test infrastructure and sample tests

Set up Vitest with @testing-library/react and jsdom for frontend
unit testing. Add sample tests for config.ts and BorderedContainer.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/justfile b/justfile
index 4825e9d..3aa5762 100644
--- a/justfile
+++ b/justfile
@@ -59,5 +59,6 @@ check:
 
 test:
     cd backend; just test
+    cd frontend; just test
+    cd worker/php; just test
     cd worker/swift; just test
-    npm -w worker/php run test