feat: add jp translation

[kevmo314]

Adds the Japanese translation file app_jp.arb to the lib/l10n directory, expanding the app's internationalization support.

• Translation Coverage: Includes comprehensive translations for UI elements, error messages, settings, and user interactions, ensuring a localized experience for Japanese users.
• User Interaction: Translates system messages, chat commands, and prompts, facilitating smoother engagement for Japanese-speaking audiences.
• Settings and Features: Localizes settings, features descriptions, and warnings, such as audio source permissions and stream preview notices, enhancing usability for the target demographic.

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For more details, open the Copilot Workspace session.

[kevmo314]

@SputNikPlop can you see if there are any japanese speakers you can run this translation file by?

[SputNikPlop]

They said quick look at it and it is fine, just line 6 is cursed