🔒 Fix WebView Mixed Content Vulnerability

[Aatricks]

🎯 What: Fixed a security vulnerability where the Cloudflare challenge WebView was configured to ALWAYS_ALLOW mixed content.

⚠️ Risk: Allowing mixed content (HTTP resources on an HTTPS page) makes the user vulnerable to Man-in-the-Middle (MitM) attacks, where an attacker could intercept or inject malicious content into the unencrypted HTTP requests, potentially compromising the session or the device.

🛡️ Solution:

1. Created a helper object WebViewUtils to encapsulate WebView configuration.
2. Changed mixedContentMode to WebSettings.MIXED_CONTENT_NEVER_ALLOW.
3. Refactored ReaderScreen.kt to use this secure helper.
4. Added a unit test to enforce this security setting.

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PR created automatically by Jules for task 5710056380815622118 started by @Aatricks

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