feat+fix(new study screen): HTML type in answer improvements

[BrayanDSO]

Fixes

• Fixes [BUG]: Modifying typed answer with JS works inconsistently #16213

Approach

1. For listening to Enter presses in the <input> box, I used onkeydown, similar to what Anki Desktop does (although they use the deprecated onkeypress listener there).
   • And I know that the screen darkens after that, but I'll fix that in the future (I think the same happens in other scenarios, but I don't recall any right now)
2. The best way I thought for the ViewModel to listen to the View (specifically the WebView in this case) was to use a CompletableDeferred Flow. I haven't tested, but it shouldn't result in any leakages, it is testable, and it doesn't couple the ViewModel with the View. It feels a bit hacky, and I suspect that this needs to be hacky, but I'm open to more elegant solutions. Maybe there are some flow or coroutines tricks that can be done.

How Has This Been Tested?

Emulator 34

Screen_recording_20251102_120321.webm

Screen_recording_20251102_120231.webm

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

[lukstbit]

Can't propose anything better so LGTM.

[mikehardy]

also LGTM