docs: add Zenith Hosting deploy option

[odpay]

hey, i work on Zenith Hosting, a startup doing one-click hosting for open source apps. we added
Unleash to our marketplace, so this PR adds a small "Deploy with Zenith" badge under the
"Deploying to a production server" section (links to https://zenith.hosting/host/unleash).

we share a cut of revenue with the projects we host. happy to explain if you're curious: hello@zenith.hosting

disclosure: this docs change was prepared with AI assistance, and reviewed before submitting.

About the changes

Closes #

Adds a "Deploy with Zenith" badge to the README's "Deploying to a production server" section, alongside the existing Heroku and DigitalOcean deploy buttons, offering readers a one-click fully managed hosting option.

Important files

• README.md

Discussion points

Docs-only change. No code, tests, or build impact.

OSS PR checklist

• I have read and agree to the Unleash Contributor License Agreement.
• I have added tests or explained why tests are not needed. (N/A: documentation-only change.)
• I have updated documentation where relevant.

[CLAassistant]

All committers have signed the CLA.

[gastonfournier]

Hi @odpay thanks for the contribution and thanks for the offering I'm going to share this with our team, but due to summer vacations our response time might be slower.

In the meantime, don't worry about the failing tests, they're just false negatives.