🛡️ Sentinel: [CRITICAL] Fix SSRF in background workers

[frkr]

🚨 Severity: CRITICAL
💡 Vulnerability: The background queue processors (MQDestiny.ts and MQCallback.ts) did not validate the protocol of user-hydrated or externally supplied URLs before making outbound fetch requests.
🎯 Impact: This lack of validation could allow Server-Side Request Forgery (SSRF). An attacker could exploit this by crafting payloads with file:, javascript:, or data: protocols, forcing the server to read local files or make arbitrary internal requests, potentially bypassing security policies.
🔧 Fix: Parsed the destination and callback URLs using the URL object and enforced a strict check to ensure their protocol is either http: or https:. If an invalid or malicious protocol is detected, the URL is rejected and the message is safely logged as 'error' in MQStore, returning early to halt execution without throwing an unhandled exception or leaking information.
✅ Verification: Ensure the test suite continues to pass (pnpm test). The fetch function will no longer execute for non-HTTP(S) URLs in background processes.

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PR created automatically by Jules for task 14747614525031795322 started by @frkr

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