🛡️ Sentinel: [MEDIUM] Add missing DoS protections to main entry point

[ManupaKDU]

🚨 Severity: MEDIUM
💡 Vulnerability: The script's __main__ entry point lacked input length limits or bounds checks for start_ip and end_ip parameters before parsing them using Python's ipaddress module, making it susceptible to resource exhaustion attacks via excessively large inputs. It also missed catching RecursionError in the parsing block, allowing specially crafted inputs to crash the process.
🎯 Impact: Attackers providing excessively long inputs could cause high CPU utilization due to the algorithmic complexity of parsing in the ipaddress module or trigger an unhandled RecursionError leading to a Denial of Service.
🔧 Fix: Explicit type checks (len() limits for strings/bytes and bound checks for integers) have been added prior to invoking ipaddress.ip_address(). RecursionError was also added to the except block alongside ValueError and TypeError.
✅ Verification: Ensure the test suite continues to pass (python3 -m unittest test_testping1.py) and manual runs of python3 testping1.py successfully scan without regressions.

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PR created automatically by Jules for task 13230402318504250777 started by @ManupaKDU

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