fix: add engines field requiring node >= 22

[Thabettt]

Added engines field to package.json specifying node >= 22.0.0. Refs apostrophecms/apostrophe#4645

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• main
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Summary

Added an engines field to package.json requiring node >= 22.0.0. This ensures users are warned about incompatible Node.js versions before installation. Refs apostrophecms/apostrophe#4645

What are the specific steps to test this change?

1. Clone the repo and run npm install with Node.js 18 — confirm the EBADENGINE warning fires
2. Run npm install with Node.js 22 or 24 — confirm no warnings appear

What kind of change does this PR introduce?

(Check at least one)

• Bug fix
• Build-related changes

Make sure the PR fulfills these requirements:

• It includes a) the existing issue ID being resolved, b) a convincing reason for adding this feature, or c) a clear description of the bug it resolves
• The changelog is updated
• Related documentation has been updated
• Related tests have been updated

Other information:
Change suggested by @boutell in apostrophecms/apostrophe#4645.

[Copilot]

Pull request overview

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Adds a Node.js runtime requirement to the project to ensure consistent execution across environments.

Changes:

• Declare a minimum supported Node.js version via package.json engines.node.

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[boutell]

Thanks!