ci: run frontend checks on any frontend change

The path filter matched only frontend/apps/remark42/**, so a change to the
workspace root ran nothing: no lint, type-check, tests or size-limit, and no
docker build either since docker.yml waits on this workflow by name.

#2160 rewrote pnpm-lock.yaml and the override block, and #2172 removed a
workspace package and its CI workflow. Neither ran a single frontend check on
its PR or on master.

.github/workflows/ci-frontend.yml

@@ -6,12 +6,12 @@ on:
       - master
     paths:
       - ".github/workflows/ci-frontend.yml"
-      - "frontend/apps/remark42/**"
+      - "frontend/**"
       - "!**.md"
   pull_request:
     paths:
       - ".github/workflows/ci-frontend.yml"
-      - "frontend/apps/remark42/**"
+      - "frontend/**"
       - "!**.md"
 
 jobs: