WKWebView: Fix Blank Screen and Prevent Memory Leaks

[yccheok]

1. Use removeScriptMessageHandlers to prevent memory leaks.

2. Recreate the web view when it turns blank.

Reference: https://nevermeant.dev/handling-blank-wkwebviews/

We avoid using a timer-based solution since it's resource-intensive. Instead, we've observed that blank issues typically occur when the app is restored from the background. Therefore, a one-time check is performed during background restoration.