🛡️ Sentinel: [HIGH] Fix timing attack vulnerabilities in token validation

[thirdeyenation]

🚨 Severity: HIGH
💡 Vulnerability: Timing attack vulnerabilities found during token, API key, and password hash validations where standard string equality operators (==, !=) were used instead of constant-time comparison functions.
🎯 Impact: An attacker could potentially use timing attacks to guess valid authentication tokens or API keys character by character, leading to unauthorized access.
🔧 Fix: Updated standard string comparisons for tokens, keys, and hashes to use secrets.compare_digest, which prevents timing attacks. Also included type checking to prevent TypeError exceptions.
✅ Verification: Verified the code changes manually and ran tests via pytest to confirm the application functions normally without regressions.

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PR created automatically by Jules for task 11445065833663479907 started by @thirdeyenation

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