feat(i18n): add Simplified Chinese (zh-Hans) localization

[DejavuMoe]

Add zh-Hans i18n support.

[Copilot]

Pull request overview

This PR adds Simplified Chinese (zh-Hans) localization to Nah.pet, providing a complete translation of all 411 messages in the application. The translation covers all user-facing text including dashboard, authentication, administration, analytics, domain management, and API response messages.

Key Changes:

• Complete Simplified Chinese translation file with all 411 message keys
• Translations for all major features: URL shortening, analytics, custom domains, admin panel, and API responses
• Proper use of Chinese punctuation and formatting conventions

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[Gradleless]

Could you add the locale in the settings.json of ParaglideJS
(see: https://github.com/anhostfr/nah.pet/blob/main/project.inlang/settings.json)?

I also created a new translation key for prohibited registration issue (auth.registration_disabled). Could you add the corresponding translation, please?

[DejavuMoe]

Could you add the locale in the settings.json of ParaglideJS (see: https://github.com/anhostfr/nah.pet/blob/main/project.inlang/settings.json)?

I also created a new translation key for prohibited registration issue (auth.registration_disabled). Could you add the corresponding translation, please?

Ok, I just finished it.

[Gradleless]

That's fine, thank you!