[Bug][Windows][i18n] Update failure message mixes Chinese and English ("fetch failed")

[shangxinyu1]

Environment

Platform: Windows
Version: Latest (0.1.10 or recent nightly builds)
Language: Chinese (zh-CN)
Affected Feature: App update / version check

Steps to Reproduce

1. Launch nexu on Windows with Chinese UI
2. Trigger an update check or app update
3. If the update fails (e.g., network error, server unreachable)
4. Observe the error message in the bottom-left notification area

Actual Behavior

The update failure notification shows mixed Chinese and English:

• Error title: "更新失败" (Chinese: "Update failed")
• Error detail: "fetch failed" (English)
• Close button: "关闭" (Chinese)

Based on the screenshot:

• A red error notification appears at bottom-left
• Shows "更新失败" as the title
• Below it displays "fetch failed" in English
• The error message is not fully localized

Expected Behavior

The entire error message should be in Chinese when the UI language is set to Chinese:

• "更新失败" (Update failed)
• "获取更新失败" or "无法下载更新" (Failed to fetch update / Unable to download update)
• Or provide a more descriptive error message like:
  • "网络连接失败，请检查网络后重试" (Network connection failed, please check your network and retry)
  • "无法连接到更新服务器" (Unable to connect to update server)

Impact

Severity: P2 (Medium) - Localization/UX issue

• Poor user experience for Chinese users
• Inconsistent localization breaks immersion
• Technical English terms ("fetch failed") are not user-friendly
• Users may not understand what "fetch failed" means
• Reduces professional appearance of the app

Suggested Fix

1. Properly localize all error messages related to update failures
2. Use descriptive, user-friendly Chinese error messages instead of technical English terms
3. Consider providing more context:
   • What failed? (Download? Connection? Verification?)
   • Why it might have failed? (Network? Server?)
   • What the user should do next? (Retry? Check network?)

Example of Good Error Messages

• ❌ Current: "fetch failed"
• ✅ Better: "获取更新失败" (Failed to fetch update)
• ✅ Best: "无法下载更新，请检查网络连接后重试" (Unable to download update, please check your network connection and retry)

Related Issues

• General i18n/localization issues in Windows version
• Error message standardization across the app

Screenshot