ci: add @vitest/coverage-v8 to workspace packages; set REDIS_URL on build

CI unit-test runs vitest run --coverage in each workspace package, but only
apps/web declared the coverage-v8 dep. In pnpm workspaces deps aren't
hoisted across packages, so engine/staffing/api/application/shared need it
directly.

The build job also needs REDIS_URL because collecting page data for
/api/perf imports a module that throws if REDIS_URL is missing under
NODE_ENV=production. A placeholder value satisfies the check (no actual
Redis connection is made at build time).

.github/workflows/ci.yml

@@ -230,6 +230,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       DATABASE_URL: postgresql://placeholder:placeholder@localhost:5432/placeholder
+      REDIS_URL: redis://placeholder:6379
       NEXTAUTH_URL: ${{ env.CI_AUTH_URL }}
       AUTH_URL: ${{ env.CI_AUTH_URL }}
       NEXTAUTH_SECRET: ${{ env.CI_AUTH_SECRET }}