feat: add language selection dropdowns to settings

[Mounil2005]

Contributor checklist

• [] This pull request is on a separate branch and not the main branch
• [] I have tested my code with the just command as directed in the testing section of the contributing guide

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Description

Adds language selection UI to the settings panel so users can choose which language to translate from and to.
Add Language enum with 8 supported languages (EN, FR, DE, IT, PT, RU, ES, SV). Add from/to language pick_list dropdowns in settings panel above theme toggle. Resize settings panel to accommodate the two additional rows.

Files changed:

1. scribe/src/state.rs: Added Language enum with 8 supported languages (English, French, German, Italian, Portuguese, Russian, Spanish, Swedish), with Display impl for dropdown labels. Added from_language and to_language fields to AppState.
2. scribe/src/lib.rs: Re-exported Language from the crate root.
3. scribe/src/bin/gui.rs: Added two pick_list dropdowns ("Translate from:" / "Translate to:") in the settings panel above the existing theme toggle. Settings panel now resizes to 160px height to accommodate the extra rows. Added FromLanguageSelected and ToLanguageSelected message variants.

Testing:
Ran cargo run --bin gui, opened settings panel, verified both dropdowns appear and are selectable.

Related issue

• Closes Make it possible to choose which language to translate to/from #20

[github-actions]

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[github-actions]

Maintainer Checklist

The following is a checklist for maintainers to make sure this process goes as well as possible. Feel free to address the points below yourself in further commits if you realize that actions are needed :)

• The CHANGELOG has been updated with a description of the changes for the upcoming release and the corresponding issue (if necessary)

[Mounil2005]

@andrewtavis Pls do let me know in case of any changes!

[andrewtavis]

@henrikth93 or @Femimat: Would one of you want to do an initial review here?

[andrewtavis]

Thanks so much for the quick work here, @Mounil2005! We'll try to bring this in in the coming days :)

[RyanPaulGannon]

@andrewtavis, would you like me to take a look? I don't want to hijack anything, just conscious I've done very little lately!

[henrikth93]

@andrewtavis, would you like me to take a look? I don't want to hijack anything, just conscious I've done very little lately!

I was just gonna reply! If you want to Ryan, you can go ahead and do a review, otherwise I can look at it! :D

[andrewtavis]

Happy to have a review here, @RyanPaulGannon :) Let's do that and then maybe @henrikth93 can review your work on #43 😊