fix: finalize UI of no language data keyboard state (#633)

[prince-0408]

Finalizes the UI for the keyboard state shown when no language data has been downloaded, addressing all design requirements outlined in the issue.

Closes #633

Changes

Area	Before	After
Scribe key	Visible alongside the button	Hidden when download button is shown
Button background (light)	scribeCTAColor with white text	scribeCTAColor (orange) with black text
Button background (dark)	Semi-transparent orange	Dark warm-brown with orange border (outlined style)
Text color	White	Black (light) / Orange (dark) for accessibility
Icon	arrow.down.circle.fill (filled)	arrow.down.circle (non-filled)
Button width	Anchored to command bar only	Full keyboard width
Dark mode updates	—	Auto-updates via traitCollectionDidChange

Implementation Details

File	Function	Change
KeyboardViewController.swift	showDownloadDataBtn()	Full restyle — colors, icon, layout, dark mode
KeyboardViewController.swift	conditionallyShowDownloadDataBtn()	Restores scribeKey.isHidden = false when button is hidden

Design Spec Checklist

Requirement	Status
Scribe key hidden in this state	✅
Black text over orange background (light mode)	✅
Dark mode version matching Scribe UI	✅
Non-filled arrow icon (arrow.down.circle)	✅

Notes

• The dark mode button uses a dark warm-brown background (#2E1F0D) with an orange border and orange text/icon — matching the outlined style shown in the design spec
• No new files added — all changes are contained in KeyboardViewController.swift
• Dark mode appearance updates automatically through the existing traitCollectionDidChange → loadKeys() → conditionallyShowDownloadDataBtn() flow, so no additional observer setup was needed

Screenshot

[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 :)

• Tests for changes have been written and the CI unit test, linting and formatting workflows within the PR checks do not indicate new errors in the files changed

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