chore(zh-CN): add missing translation keys across 6 files

[LifetimeVip]

Summary

Adds ~60 missing zh-CN translation keys across 6 files that exist in the English source but were absent from the Simplified Chinese translation.

Files changed

chat.json (+6 keys)

• plugins/pluginSelect/cancelMcpAuthentication/error: 取消插件认证失败
• plugins/pluginSelect/signOutMcpPlugin/error: 退出插件登录失败
• genInfo speculative decoding stats
• actions/clearLastUsedModel and error message

config.json (+10 keys)

• llm/load/numCpuExpertLayersRatio (title, subTitle, info)
• llm/load/numParallelSessions (title, subTitle)
• llm/load/useUnifiedKvCache (title, subTitle)
• presets/saveChanges section

developer.json (+17 keys)

• New API endpoints: lmStudioRestV1, openaiCompatRest/postResponses
• serverOptions/allowMcp section (all modes and hints)
• Endpoint labels for Anthropic/OpenAI/LM Studio

models.json (+15 keys)

• Model loading guardrails with memory warnings
• virtual/altsSelect section for model variants
• indexingPageLoaderText

settings.json (+14 keys)

• Navigation bar position options
• Default context length section (custom/max values, warnings)
• jitTTL/subtitle and model defaults

shared.json (+1 key)

• beta label

Verification

All JSON files pass validation. Changes are additions only - no existing translations were modified or removed.

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[LifetimeVip]

退下，换更完整的 PR