Deprecate Photon repository and redirect users to universal-deploy

[Copilot]

This repository is now deprecated in favor of universal-deploy, per issue #72. The root documentation now makes that status explicit so users immediately see the migration path.

• Deprecation banner update
  • Replaced the existing beta warning in the root README with a deprecation notice.
  • Added direct links to the successor repository and the tracking issue to reduce ambiguity for new and returning users.

> [!WARNING]
> **Deprecated**: This repository is deprecated in favor of [universal-deploy](https://github.com/universal-deploy/universal-deploy). See [issue #72](https://github.com/photon-js/photon/issues/72).

[changeset-bot]

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Latest commit: 903d744

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Project	Deployment	Actions	Updated (UTC)
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