feat: add Chinese i18n support with vue-i18n

[WanderLandWalker]

This PR adds Chinese (zh) language support to ActivityWatch:

• Installs vue-i18n for Vue 2
• Creates en.json and zh.json locale files
• Replaces hardcoded English strings with () calls across all views and components
• Adds language switcher in Settings → Theme
• Persists language preference to localStorage
• Auto-detects browser language on first visit
• Adds Chinese translations for README, CODE_OF_CONDUCT, CONTRIBUTING with language switcher badges

[greptile-apps]

Greptile Summary

This PR adds Chinese (Simplified) language support to ActivityWatch's documentation by introducing Chinese translations of README, CODE_OF_CONDUCT, and CONTRIBUTING, and appending shields.io language-switcher badges to each existing English file.

• Three new Chinese Markdown files (README.zh.md, CODE_OF_CONDUCT.zh.md, CONTRIBUTING.zh.md) provide full translations, including a translated Mermaid architecture diagram and comparison tables.
• Three existing English files (README.md, CODE_OF_CONDUCT.md, CONTRIBUTING.md) each receive a single two-badge language-switcher line at the top using proper shields.io image URLs.
• Two internal cross-links in the Chinese files still point to the English originals instead of the newly added Chinese versions.

Confidence Score: 5/5

Safe to merge — all changes are documentation only, with no impact on application code or runtime behaviour.

The entire diff is additive Markdown content. The three existing files receive only two new badge lines each, and the three new Chinese translation files are standalone documents. No application logic, build configuration, or data is touched.

README.zh.md and CONTRIBUTING.zh.md contain cross-links that point to the English versions of documents that now have Chinese translations.

Important Files Changed

Filename	Overview
README.md	Adds two lines of shields.io language-switcher badges at the top; no other changes to existing content.
README.zh.md	New full Chinese translation of the README; cross-link in the contribution section points to English CONTRIBUTING.md instead of CONTRIBUTING.zh.md.
CODE_OF_CONDUCT.md	Adds two lines of shields.io language-switcher badges at the top; no other changes to existing content.
CODE_OF_CONDUCT.zh.md	New Chinese translation of the Code of Conduct; content is complete and all links are correct.
CONTRIBUTING.md	Adds two lines of shields.io language-switcher badges at the top; no other changes to existing content.
CONTRIBUTING.zh.md	New Chinese translation of the contributing guide; the code-of-conduct section links to English CODE_OF_CONDUCT.md instead of CODE_OF_CONDUCT.zh.md.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[User opens README.md / README.zh.md] --> B{Language badge clicked?}
    B -- "en badge" --> C[README.md]
    B -- "zh-CN badge" --> D[README.zh.md]
    C --> E{Internal link clicked?}
    D --> F{Internal link clicked?}
    E -- CONTRIBUTING link --> G[CONTRIBUTING.md]
    E -- CODE_OF_CONDUCT link --> H[CODE_OF_CONDUCT.md]
    F -- CONTRIBUTING link --> I[CONTRIBUTING.md - should be .zh.md]
    G --> K{Language badge?}
    K -- zh-CN --> L[CONTRIBUTING.zh.md]
    L -- CODE_OF_CONDUCT link --> M[CODE_OF_CONDUCT.md - should be .zh.md]

Loading

_{Reviews (3): Last reviewed commit: "fix: use shields.io badges for language ..." | Re-trigger Greptile}

[greptile-apps]

Untranslated tagline in Chinese README

The introductory paragraph retained its English text (Records what you do…, All in a secure way…) and was never translated. A reader looking at this file for a Chinese-language version will encounter English text immediately below the banner, undermining the purpose of the translation.

[greptile-apps]

The badge syntax [![en](README.md)](/README.md) uses a Markdown file path as the image source. GitHub cannot render a .md file as an image, so both badges will display as broken-image icons. Use shields.io URLs (or plain text links) instead so the language switcher actually renders.

Suggested change

	[](/README.md) | [](/README.zh.md)
	[](/README.md) | [](/README.zh.md)

[greptile-apps]

Same broken-image badge issue as in README.md — .md files cannot be used as image sources in Markdown badge syntax, so this switcher will display broken icons on GitHub.

Suggested change

	[](/CODE_OF_CONDUCT.md) | [](/CODE_OF_CONDUCT.zh.md)
	[](/CODE_OF_CONDUCT.md) | [](/CODE_OF_CONDUCT.zh.md)

[greptile-apps]

Same broken-image badge issue — .md files cannot serve as image sources, so both language switcher badges will render as broken icons on GitHub.

Suggested change

	[](/CONTRIBUTING.md) | [](/CONTRIBUTING.zh.md)
	[](/CONTRIBUTING.md) | [](/CONTRIBUTING.zh.md)

[greptile-apps]

The badge format here differs from CODE_OF_CONDUCT.zh.md and CONTRIBUTING.zh.md. The outer wrapper [... | ...](README.zh.md) creates a single link around both images (with a literal pipe character), and the "English" badge also has a broken image source. The other Chinese files correctly use two independent clickable badge links separated by |. Additionally all image sources should be shields.io URLs.

Suggested change

	[ | ](README.zh.md)
	[](/README.md) | [](/README.zh.md)

[greptile-apps]

Same broken-image badge issue — CODE_OF_CONDUCT.md and CODE_OF_CONDUCT.zh.md are not image files and will render as broken icons on GitHub.

Suggested change

	[](/CODE_OF_CONDUCT.md) | [](/CODE_OF_CONDUCT.zh.md)
	[](/CODE_OF_CONDUCT.md) | [](/CODE_OF_CONDUCT.zh.md)

[greptile-apps]

Same broken-image badge issue — CONTRIBUTING.md and CONTRIBUTING.zh.md are not image files and will render as broken icons on GitHub.

Suggested change

	[](/CONTRIBUTING.md) | [](/CONTRIBUTING.zh.md)
	[](/CONTRIBUTING.md) | [](/CONTRIBUTING.zh.md)

[ant-cave]

Yes, I really need this feature too.

[0xbrayo]

@greptile-apps review