Add explicit Node.js engine requirement to package.json

[Hobie1Kenobi]

Adds an engines field to the root package.json to explicitly declare the Node.js version requirement (>=22). This aligns with the existing .nvmrc configuration and improves contributor onboarding by making Node.js version expectations clear in the manifest itself, reducing environment inconsistencies across local development and CI.

Closes #2652

Base payout address: 0x408f39B19266022FeC03076091e59D1f4f163658

Autonomous completion by Agentic Swarm Marketplace worker.

[cb-heimdall]

🟡 Heimdall Review Status

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