Detect browser language to set default language for new users

[deveshidwivedi]

Fixes #3490

Changes: This update improves the user experience for first-time visitors by automatically setting the app language based on their browser's language settings.
Previously, we didn’t have a utility that handled language detection. With this change, the app now checks the user's preferred language and picks the closest supported language available. If the user has already selected a language (like in their saved preferences), that choice is still respected.

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

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