feat(web): enable app locales and add language toggle

[cungminh2710]

What changed

Promote ready content locales (zh-CN, vi-VN, de-DE, fr-FR) into SUPPORTED_APP_LOCALES so routing, cookies, sitemap, and robots cover them. Add a LocaleToggle beside ThemeToggle on the marketing navbar and in the app shell. Includes the approved ADR.

How to test

• Open marketing or app shell and switch language via the new toggle; confirm URL prefix and UI locale update
• Confirm /zh-CN/..., /vi-VN/..., /de-DE/..., /fr-FR/... routes resolve
• Spot-check sitemap.xml and robots.txt include the new locales
• From apps/hyperlocalise-web: vp test src/lib/app-i18n/ and vp check --fix

Checklist

• I ran relevant checks locally (vp check --fix; locale-related vp test)
• I updated docs, comments, or examples when needed
• This PR is scoped and ready for review

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
hyperlocalise	Ignored		Jul 10, 2026 1:40am

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[greptile-apps]

Greptile Summary

This PR enables more app locales and adds a language switcher. The main changes are:

• Promotes ready content locales into supported app locales.
• Adds a LocaleToggle to marketing and app-shell navigation.
• Adds locale path rewrite helpers and tests.
• Documents the locale support and selector design in an ADR.

Confidence Score: 5/5

This looks safe to merge after a small locale-toggle cleanup.

• The expanded locale list follows the existing routing and provider patterns.
• The new switcher has one small state-source mismatch that can produce an incorrect URL in fast navigation cases.
• No blocking issues were found in the changed code.

apps/hyperlocalise-web/src/components/locale-toggle/locale-toggle.tsx

Important Files Changed

Filename	Overview
apps/hyperlocalise-web/src/components/locale-toggle/locale-toggle.tsx	Adds the client language dropdown and locale-switch navigation.
apps/hyperlocalise-web/src/lib/app-i18n/rewrite-app-locale-path.ts	Adds helpers for reading and rewriting app locale prefixes.
apps/hyperlocalise-web/src/lib/app-i18n/locales.ts	Expands supported app locales to match available content locales.
apps/hyperlocalise-web/src/app/[lang]/(marketing)/_components/navbar.tsx	Adds the language toggle next to the existing theme controls.
apps/hyperlocalise-web/src/components/app-shell/app-shell-client.tsx	Adds the language toggle to the authenticated app shell header.

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
apps/hyperlocalise-web/src/components/locale-toggle/locale-toggle.tsx:65
**Mixed Router And Window State**

When the user changes language during or immediately after a client-side navigation, `pathname` can come from the App Router state while `window.location.search` and `window.location.hash` still come from the current browser URL. That can combine the next route with stale query or hash state, so the language toggle can navigate to the wrong localized URL or preserve filters/anchors from the previous page.

_{Reviews (1): Last reviewed commit: "feat(web): enable app locales and add la..." | Re-trigger Greptile}

[greptile-apps]

Mixed Router And Window State

When the user changes language during or immediately after a client-side navigation, pathname can come from the App Router state while window.location.search and window.location.hash still come from the current browser URL. That can combine the next route with stale query or hash state, so the language toggle can navigate to the wrong localized URL or preserve filters/anchors from the previous page.

Prompt To Fix With AI

This is a comment left during a code review.
Path: apps/hyperlocalise-web/src/components/locale-toggle/locale-toggle.tsx
Line: 65

Comment:
**Mixed Router And Window State**

When the user changes language during or immediately after a client-side navigation, `pathname` can come from the App Router state while `window.location.search` and `window.location.hash` still come from the current browser URL. That can combine the next route with stale query or hash state, so the language toggle can navigate to the wrong localized URL or preserve filters/anchors from the previous page.

How can I resolve this? If you propose a fix, please make it concise.