chore: Add GitHub Actions CI for web packages

[jade-codes]

Description

Add CI workflow for the web packages using Bun.

Tasks

• Create .github/workflows/ci-frontend.yml
• Trigger on packages/** changes
• Steps: checkout, setup Bun, bun install, lint, type-check, test, build
• Cache Bun dependencies (~/.bun/install/cache)

Acceptance Criteria

• Workflow runs on PRs touching web/ folder
• All checks pass on empty scaffold
• Caching works for fast subsequent runs