feat(backend): Use milliseconds instead of seconds for M2M token nomenclature

[alexisintech]

Description

Related Slack conversation: https://clerkinc.slack.com/archives/C01QFRQNHSN/p1767646570366689

M2M token timestamps are in milliseconds, not seconds. This PR updates the nomenclature to be more clear.

Checklist

• pnpm test runs as expected.
• pnpm build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

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Latest commit: 318a158

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Project	Deployment	Review	Updated (UTC)
clerk-js-sandbox	Ready	Preview, Comment	Jan 6, 2026 0:05am

[alexcarpenter]

@alexisintech since you are targeting main here which is the core-3 branch, you could just make the change and avoid the depreciation notice.

Then you can make these changes on core-2 branch with the deprecation notice there.

[alexisintech]

closing in favor of: feat(api-keys,m2m-tokens): Add descriptions to schemas regarding timestamp units