[Improvement] Add CI job timeouts and caching for faster builds

[d-oit]

Description

Missing CI Timeouts

No timeout-minutes is set on any CI job. GitHub Actions defaults to 6 hours, which means a hung job could burn 360 minutes of CI time. Per LESSON-013 in agents-docs/LESSONS.md, this has already caused issues.

Missing Caching

No caching for:

• pnpm store across CI runs
• node_modules
• Playwright browser binaries
• Vite build cache

Other CI Issues

• No path-based job skipping (all changes trigger full CI)
• No code coverage reporting in CI (test:coverage script exists but is not run)
• dependabot.yml configured for Docker, Terraform, Docker Compose, pre-commit — none of which exist in this repo
• create-jules-issues.yml is a one-time workflow that should be disabled/removed

Recommended Fix

1. Add timeout-minutes: 15 to all CI jobs
2. Add pnpm store caching: actions/cache with ~/.local/share/pnpm/store
3. Add Playwright browser caching
4. Add path filters to skip CI on docs-only changes
5. Remove Dependabot ecosystems that do not exist in the repo
6. Add coverage reporting step
7. Disable or remove create-jules-issues.yml

Acceptance Criteria

• All CI jobs have timeout-minutes
• pnpm store cached between runs
• Playwright browsers cached
• Dependabot only configured for existing ecosystems
• Coverage reported in CI
• create-jules-issues.yml disabled or removed