feat(backend, clerk-js): Support origin outage mode

[bratsos]

Description

Checklist

• [x] pnpm test runs as expected.
• [x] 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:

Summary by CodeRabbit

• New Features

  • Added origin outage mode support for improved reliability during token expiration scenarios, enabling automatic retry with last active token when applicable.

• Tests

  • Added comprehensive test coverage for origin outage fallback behavior and token retry logic.

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