fix(react): refresh i18n context identity for React Compiler memoization

[yslpn]

Description

Recreate i18n reference in I18nProvider via Proxy so memoized React Compiler paths update on locale change.
Add a regression test for memoized useLingui().i18n locale updates.

Avoiding recreating the initial state of the context by passing a function to useState
https://react.dev/reference/react/useState#avoiding-recreating-the-initial-state

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Examples update

Fixes #2343

Checklist

• I have read the CONTRIBUTING and CODE_OF_CONDUCT docs
• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary documentation (if appropriate)

[vercel]

@yslpn is attempting to deploy a commit to the Crowdin Team on Vercel.

A member of the Team first needs to authorize it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.66%. Comparing base (dd43fb0) to head (133db5f).
⚠️ Report is 312 commits behind head on next.

Additional details and impacted files

@@             Coverage Diff             @@
##             next    #2456       +/-   ##
===========================================
+ Coverage   76.66%   88.66%   +11.99%     
===========================================
  Files          81      117       +36     
  Lines        2083     3308     +1225     
  Branches      532      975      +443     
===========================================
+ Hits         1597     2933     +1336     
+ Misses        375      337       -38     
+ Partials      111       38       -73     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.