fix(cloudflare): send named addresses as objects

[muco-rolle]

🔗 Linked issue

Closes #184

❓ Type of change

• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The Cloudflare transport sent a named address as a "Name <email>" string. Cloudflare's send API only accepts printable ASCII in a plain string (email-sending_EmailAddressString, pattern ^[\x20-\x7E]+$), so a name like Équipe RH was refused with 400 · 10001 email.sending.error.invalid_request_schema.

Named addresses are now sent as { address, name } objects (email-sending_EmailAddressObject), which the API accepts for from, to, cc, bcc and reply_to. Addresses without a name are still sent as plain strings. The comment on #formatRecipients is updated, since the schema settles the address key it was unsure about.

The existing recipients test now expects objects, and a new test covers a non-ASCII name. The Cloudflare tests pass; the rest of the suite is unchanged (the integration tests that need provider credentials fail the same way on 10.x locally).

Recipients given as "Name <email>" strings are still forwarded as is, like in the other JSON transports, and Brevo and SparkPost would need the same treatment. Happy to send a follow-up that parses them with Nodemailer's addressparser if you think it's worth it.

📝 Checklist

• I have read the contribution guide.
• I have linked an issue or discussion.
• I have updated the documentation accordingly.