feat: add CI workflows #24

Description

Add CI workflow files for automated checks, dependency review, and security scanning.

Acceptance Criteria

• .github/workflows/ci_checks.yml created:
  • Triggers: push to main, PR to main
  • Lint job: go vet ./..., yamllint on org/config.yaml and safe-settings/
  • Test job: go mod tidy, go mod vendor, git diff --exit-code, go test -race -v -coverprofile=coverage.out ./...
  • Actions pinned: checkout@3d3c42e5 (v7.0.1), setup-go@b7ad1dad (v7.0.0)
• .github/workflows/ci_dependencies.yml created:
  • Trigger: PR to main
  • Uses actions/dependency-review-action@da24556b (v4.7.1)
• .github/workflows/ci_security.yml created:
  • Triggers: push to main, PR to main
  • OSV-Scanner (google/osv-scanner-action@e5012758 v2.0.2)
  • OpenSSF Scorecards (ossf/scorecard-action@05b42c62 v2.4.2) with SARIF upload
• .github/workflows/ci_scheduled.yml created:
  • Trigger: daily cron (0 0 * * *)
  • Same OSV-Scanner and Scorecards scans as ci_security
• All workflows use owner-based guards: github.repository_owner == 'unbound-force'

References

• Modeled on: zero-dot-force/.github/.github/workflows/ci_*.yml