feat: Add Conjugate tab to Conjugate app (#563)

[Mounil2005]

Contributor checklist

• This pull request is on a separate branch and not the main branch
• I have tested my code with the ./gradlew lintKotlin detekt test command as directed in the testing section of the contributing guide

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Description

This PR introduces the "No Data" empty state for the Conjugate App tab, enabling users to download the necessary conjugation data before proceeding.

Key Changes:

• ConjugateScreen.kt
  (New): Adds the "No Data" UI for the Conjugate Tab, reusing the keyboard's download button (DownloadDataOptionComp) for consistent styling. Includes Android Studio previews.
• ConjugateViewModel.kt
  (New): Tracks data availability (isDataAvailable) to switch between the empty state and the future conjugation UI.
• App.kt: Replaces the placeholder text with ConjugateScreen, connecting it to the app's existing theme and download logic.

Testing:

• Verified Gradle build succeeds without AAPT2 duplication errors on string resources.
• Verified @Preview components render the expected Light and Dark mode variations accurately directly in Android Studio.

Related issue

Closes #563

[github-actions]

Thank you for the pull request! 💙🩵

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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 unit test, linting and formatting workflows within the PR checks do not indicate new errors in the files changed

  • Tests may need to be reran as they're at times not deterministic

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

[Mounil2005]

Hey @andrewtavis pls let me know in case of any changes!