chore: enhance CI with linting and whitespace checks in GitHub Actions

[akrem-chabchoub]

summary

Align beekeeper CI with ethersphere/bee: conventional commit lint on PRs, PR title lint, and extra quality checks (whitespace + go mod tidy). Splits lint onto Ubuntu only and keeps build/test on the OS matrix.

changes

• add commitlint.config.js at repo root (@commitlint/config-conventional rules, header max length 98)
• add .github/workflows/pr-title.yml — lint PR title on opened, synchronize, reopened, edited
• update .github/workflows/go.yml:
  • pull_request with paths-ignore: '**/*.md' for the Go workflow
  • new lint job: full history checkout, wagoid/commitlint-github-action@v5, golangci-lint, make vet, make check-whitespace, katexochen/go-tidy-check@v2
  • build job: matrix build + test only (shallow checkout)
• add check-whitespace target to Makefile (same idea as bee)
• fix existing trailing whitespace / EOF whitespace issues so the new check passes

why

Keeps commit and merge messages consistent across swarm repos and catches bad titles/commits before merge.

notes

• Markdown-only PRs skip the Go workflow but still get PR title lint.
• Update branch protection if you want Lint and Lint PR Title required.

Refs: ethersphere/bee go.yml, pr-title.yml, commitlint.config.js.