Improve error handling on existing seed view

[bgptr]

This diff improves the error handling on the existing seed view by changing the input's border color to red if the seed word is not at valid position.

[vctt94]

Thanks for this PR.

I left a couple of comments, but I like the direction this is going.

[bgptr]

Thank you for your review. I fixed your comments.

[vctt94]

Thanks for fixing my comments.

I have a couple more comments.

I noticed it is possible when entering a word in its wrong place, the wallet throws an error, but it does not show right after it. It only shows after you entering the next word, example:

Here the absurd word already errored, as you can see at decrediton logs:

But it only shows as wrong if I add the third word:

And if I delete the word from its position, the field border gets missed:

I also think it would be good keeping the error message instead of just making the word red, as it can be a bit confusing. Making it red and showing an error message like "word on position n is wrong" would make it clearer. What do you think?

[bgptr]

Thank you for your review. I fixed the mentioned issues and cleaned up the component a bit. Also, I added the suggested error message. It is much more straightforward now.

[vctt94]

LGTM. Good job on this PR!