🛡️ Sentinel: [HIGH] Fix timing attack and information disclosure in internal router

[ivanleekk]

🚨 Severity: HIGH

💡 Vulnerability:

1. The scheduler secret verification was using a standard string comparison !=, which is susceptible to timing attacks.
2. The catch-all exception block for daily snapshots was leaking raw stack traces/details str(e) to the client, leading to information disclosure.

🎯 Impact:

1. An attacker could potentially infer the secret character-by-character based on the response time.
2. An attacker could gain internal knowledge about the database or server state via error messages.

🔧 Fix:

1. Replaced the != comparison with secrets.compare_digest for constant-time comparison, handling cases where the secret is None.
2. Stripped str(e) from the HTTPException detail, replacing it with a generic error message, and implemented logger.error to keep the original stack trace on the server side for observability.

✅ Verification:
Ran ruff check on the internal router and backend test suite successfully, verifying that the fix introduces no linting errors or regressions.

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PR created automatically by Jules for task 9391083385620331828 started by @ivanleekk

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