Improve UX for resolving 'Han Unification' rendering issues

A common issue which learners face is:

**Why does my Kanji render as Hanzi**

This is caused by a Unicode concept: [Han Unification](https://en.wikipedia.org/wiki/Han_unification)

For these characters to render correctly, a `lang=ja` attribute needs to be added to the HTML for a Japanese learner

Example

```html
U+9AA8
骨
骨
骨
骨
骨
```

renders as

**Steps to Resolve**

1. **Detect**: figure out if a character is in the set of 'badly unified' chars
* Ensure it hasn't been disambiguated already
2. What to do?
* Initially: possibly open up a help page?
* Probably an 'ignore' for when the user doesn't care
* Maybe an 'auto-fix' button for the general 'basic' note type case

I'd accept a 'stage 1' fix as writing code to detect the issue, there's a brief UX discussion on how we improve the UX

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Originally posted as https://github.com/ankidroid/Anki-Android/issues/19150#issuecomment-3240453441