🛡️ Sentinel: [HIGH] Fix SSRF vulnerability in background workers

[frkr]

🚨 Severity: HIGH
💡 Vulnerability: Server-Side Request Forgery (SSRF) vulnerability in background workers processing messages. The workers blindly passed asyncContent.destiny and asyncContent.callback to fetch() without verifying the URL protocol. This meant that an attacker who managed to queue an asynchronous message could supply a non-HTTP URL (like file://, ftp://, etc.) causing the worker to interact with internal or unexpected external systems.
🎯 Impact: High. Depending on the Cloudflare Worker runtime restrictions or eventual deployment context, fetching unintended protocols or internal endpoints can lead to data leakage, bypassing network access controls, and probing internal infrastructure.
🔧 Fix:

• Handled potential errors when parsing URLs by wrapping new URL() in a try/catch block.
• Implemented protocol validation ensuring that the URL uses the http: or https: scheme.
• If an invalid or unallowed protocol is detected, the message state is immediately set to 'error' and processing returns early, preventing infinite loops and dangerous operations.
  ✅ Verification: Tested against the full test suite (pnpm test), ensuring that 12 test files passed successfully, without regressions.

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PR created automatically by Jules for task 1502159186315946944 started by @frkr

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