feat(i18n): update translations for simplified chinese

[Andepthy]

Description

Completed missing Simplified Chinese translation keys based on English JSON.

Checklist

• PR title follows Conventional Commits (type(scope): description)
• I have run pnpm lint before raising this PR
• I have run pnpm format before raising this PR

[coderabbitai]

📝 Walkthrough

Walkthrough

The Chinese locale adds and updates translations for web promotion, sharing, device pairing, system integration, relay settings, updater notifications, pairing verification, and transfer history.

Changes

Chinese locale updates

Layer / File(s)	Summary
Sharing and transfer strings frontend/src/locales/zh-CN/common.json	Adds and updates Chinese strings for sharing, pairing, receiving, downloads, transfer status, errors, and previews.
Device, system, and relay settings frontend/src/locales/zh-CN/common.json	Adds translations for startup, tray actions, device management, discovery, relay documentation, and relay fallback policies. Removes obsolete duplicate device-settings strings.
Updater, notifications, and transfer history frontend/src/locales/zh-CN/common.json	Adds updater messages, system notifications, pairing verification, transfer-history views, filters, statuses, empty states, and history settings.

Suggested reviewers: tonyantony300

Merge Risk: ⚪ Minimal · up to 19c84

The PR only updates Simplified Chinese copy; a few strings remain grammatically incorrect or incomplete, but the issue is localized to translation quality and does not affect application behavior. No actionable merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 1

✅ Passed checks (1 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

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Actionable comments posted: 2

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: cf3d5526-e5cc-4610-85e7-cf4c99f9907e

📥 Commits

Reviewing files that changed from the base of the PR and between b2df308 and 19c8440.

📒 Files selected for processing (1)

• frontend/src/locales/zh-CN/common.json

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