Fix: Make Image insert screen WebView background transparent

[Ratnesh5]

Purpose / Description

By default, the image insert screen's WebView renders with a white background. This caused the background to clash with the app's theme and look glaringly out of place, especially in dark mode.

Fixes

• Fixes Image insert screen WebView does not match app background #21820

Approach

To address this, we need the WebView to have a transparent background so that the underlying app theme's background shows through seamlessly.

• Overrode setBackgroundColor(color: Int) in SafeWebViewLayout so it applies the color to its internal WebView.
• Set the multimediaWebView background to Color.TRANSPARENT in MultimediaImageFragment during setupWebView().

Below is the attached screenshot of before and after

How Has This Been Tested?

• Built and ran the app on an Android emulator/device.
• Toggled Dark Mode on.
• Navigated to the Note Editor and selected the attachment icon to insert an image.
• Verified that the image preview screen's background is now properly transparent and seamlessly blends in with the dark theme.

Checklist

Please, go through these checks before submitting the PR.

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[david-allison]

Would it be feasible for you to add a @NeedsTest or a screenshot test for this, so we catch future regressions?

Code looks good, thanks!

[Ratnesh5]

Would it be feasible for you to add a @NeedsTest or a screenshot test for this, so we catch future regressions?

Done! Added the @NeedsTest annotations where the background color is set. Thanks for the review!

[david-allison]

Cheers