🛡️ Sentinel: [CRITICAL] Fix timing attack vulnerabilities in authentication

[thirdeyenation]

🚨 Severity: CRITICAL
💡 Vulnerability: Simple string comparisons (== and !=) were used across multiple core modules (helpers/api.py, helpers/ui_server.py, helpers/ws.py, helpers/fasta2a_server.py, plugins/_telegram_integration/api/webhook.py) for validating sensitive authentication hashes, API keys, CSRF tokens, and webhook secrets. This exposes these endpoints to timing attacks.
🎯 Impact: Attackers could theoretically infer valid tokens character by character by measuring the exact processing time taken by the server to reject incorrect tokens, potentially bypassing authentication or CSRF protections.
🔧 Fix:

• Replaced all instances of simple string comparisons for security tokens with secrets.compare_digest().
• Ensured type safety by robustly casting operands to strings and handling None values (e.g., str(val or "")) to prevent TypeError exceptions.
• Added top-level import secrets to modified files where necessary.
  ✅ Verification: Verified syntax using py_compile across all modified files. Tests fail globally due to missing dependencies in the execution environment, but compilation checks pass, confirming structural integrity.

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PR created automatically by Jules for task 6133551079142345808 started by @thirdeyenation

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