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

[frkr]

🚨 Severity: HIGH

💡 Vulnerability: The background queue workers (src/mq/MQDestiny.ts and src/mq/MQCallback.ts) were parsing URLs dynamically derived from queue messages and passing them directly into fetch() calls without explicitly validating the URL protocol (scheme). Because new URL() simply validates structural soundness, an attacker could supply file://, ftp://, or other non-HTTP schemes in the queue payload.

🎯 Impact: This enables Server-Side Request Forgery (SSRF). While Cloudflare Workers environments mitigate some standard node-based file:// risks, allowing unvalidated protocols in backend fetching services can lead to arbitrary probing, interacting with internal metadata endpoints, or bypassing network restrictions/egress filters.

🔧 Fix: I introduced explicit URL protocol validation directly after new URL() parsing in both background workers. If the protocol is not strictly http: or https:, the worker throws an error, fails securely, and updates the queue message status to 'error' using MQStore, effectively stopping the bad request and preventing infinite retry loops.

✅ Verification:

• Added the URL protocol strict validation.
• All unit tests (pnpm test) executed and passed successfully.
• Code changes reviewed to ensure safe fallbacks.
• Documented learning in .jules/sentinel.md.

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PR created automatically by Jules for task 620201129246789358 started by @frkr

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