Add Nepali Translation

[Sahilverse]

Before Submitting This PR

Please confirm you have done the following:

• I have searched existing issues and pull requests (including closed ones) to ensure this isn't a duplicate
• I have read CONTRIBUTING.md

Human Written Description

This PR adds Nepali translations for all user interface strings in Handy.

Testing

• Terminology standardized against Google's shipped Nepali translations, verified empirically by term-frequency analysis of Chromium's generated_resources_ne.xtb and AOSP Settings values-ne/strings.xml: हिस्ट्री (History), कपी गर्नुहोस् (Copy), डिभाइस (device), सेभ गर्नुहोस् (Save), मेटाउनुहोस् (Delete), उन्नत (Advanced), साउन्ड (Sound section), "X अन गर्नुहोस्" (Enable X), "…गर्न सकिएन" passive error phrasing, "…गरिँदैछ" progressive statuses. Grammar follows the Microsoft Nepali Localization Style Guide: danda (।) sentence ends, honorific तपाईं/गर्नुहोस् forms, everyday word choices.
• bun run scripts/check-translations.ts — reports ✓ NE: All keys present (378/378 keys, matching en exactly).
• Verified all {{variables}} (e.g. {{error}}, {{model}}, {{total}}) are preserved unchanged in every translated string.
• Brand/product names (Handy, Whisper, Parakeet, Moonshine, transcribe.cpp, ggml, OpenAI, GitHub, API, GPU, VAD) kept untranslated per the guidelines.
• Ran bun run tauri dev, set Application Language to नेपाली (Settings → General → App Language), and verified Devanagari rendering across onboarding, General, Models, Advanced, History, and About screens.
• bun run lint passes; prettier --check passes on the new file.

AI Assistance

• No AI was used in this PR
• AI was used (please describe below)

If AI was used:

• Tools used: Claude Code
• How extensively: Claude generated the initial Nepali translation and registered the language in languages.ts. Then, I reviewed and standardized the terminology against Google's shipped Nepali translations and the Microsoft Nepali Localization Style Guide, making corrections to grammar, punctuation, and word choice.

[cjpais]

Thank you! New translations always appreciated