🛡️ Sentinel: [CRITICAL] Add authentication to user admin routes and fix sync crypto DoS

[aperetti]

🚨 Severity: CRITICAL
💡 Vulnerability: The usersRoutes in the admin console backend (admin-console/admin-backend/src/features/users/routes.ts) lacked any authentication, exposing sensitive administrative actions (listing, creating, deleting users) to public access. Furthermore, password verification was vulnerable to timing-based discovery and lacked proper length checks before crypto.timingSafeEqual, which throws TypeError on mismatched buffer sizes.
🎯 Impact: Unauthorized individuals could trivially compromise the system by viewing the list of existing administrative users and forging their own admin credentials or deleting existing ones. Exploiting the timingSafeEqual length mismatch would cause an unhandled exception, repeatedly crashing the admin backend (Denial of Service).
🔧 Fix: Added a Fastify onRequest hook applying HTTP Basic Authentication to the usersRoutes scope. The authentication properly checks the Authorization header, retrieves the user from the database, asynchronously derives the key using pbkdf2Async, and compares it securely with crypto.timingSafeEqual ensuring lengths match first. Corrected the base64 parsing logic to properly handle passwords that may legitimately contain colon (:) characters.
✅ Verification: Verified by running npx tsc --noEmit and vitest in the admin-console/admin-backend directory resulting in 0 errors and 0 test failures.

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PR created automatically by Jules for task 17808494147750802462 started by @aperetti

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