Implement Cloudflare DNS API provider

[antaloaalonso]

Summary

• replace the Cloudflare DNS stub with real Cloudflare API v4 calls for zones, records, upserts, deletes, and round-robin sync
• map Cloudflare response fields into sh1pt DNS records and support account filters, pagination, TTL defaults, and proxied defaults
• add mocked API coverage for auth, pagination, record mapping, create/update/delete, round-robin reconciliation, and API error messages

Related to #6.

Validation

• corepack pnpm@9.12.0 --filter @profullstack/sh1pt-dns-cloudflare typecheck
• corepack pnpm@9.12.0 exec vitest run packages/dns/cloudflare/src/index.test.ts
• corepack pnpm@9.12.0 --filter @profullstack/sh1pt-dns-cloudflare build
• corepack pnpm@9.12.0 --filter @profullstack/sh1pt typecheck
• git diff --check

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.