🛡️ Sentinel: [security improvement] Add input length limits

[scartill]

🚨 Severity: MEDIUM
💡 Vulnerability: The pyparsing implementation is susceptible to Denial of Service (DoS) attacks via CPU exhaustion when processing extremely long strings for principal, resource, or action parameters.
🎯 Impact: An attacker could pass a massive string to the authorization check, causing the CPU to block for extended periods (e.g., >40 seconds for a 200KB string) and crashing or degrading service performance.
🔧 Fix: Implemented maximum length limits on user-controlled inputs before processing: 2048 characters for principal and resource, and 256 characters for action. If exceeded, TagthValidationError is raised securely.
✅ Verification: Covered by test_input_length_limits unit tests inside test/test_allowed.py.

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PR created automatically by Jules for task 1534768833717533960 started by @scartill

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