feat: spikes 645-648 (SEP-50, cross-chain verification, explorer integration) - #576

Dependencies lock file is not found in /home/runner/work/Phase/Phase. Supported file patterns: yarn.lock

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/