🔒 Fix XXE vulnerability in PersistentSettings

[ManupaKDU]

🎯 What: The PersistentSettings.cs file was vulnerable to XML External Entity (XXE) injection when loading configuration files via XmlDocument.
⚠️ Risk: An attacker who can control or manipulate the contents of the configuration file could potentially read arbitrary local files, cause a denial of service (DoS) by initiating large/infinite entity expansions (billion laughs attack), or execute Server-Side Request Forgery (SSRF) if the machine tries to fetch an external URI specified in the XML document entity.
🛡️ Solution: The fix sets the XmlResolver property on the XmlDocument object to null before loading the XML payload. This explicitly disables the resolution of external entities, which eliminates the XXE vulnerability.

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PR created automatically by Jules for task 418914612367225023 started by @manupawickramasinghe

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