Fix incorrect locale casing for pt-BR #1501

[codeWithPunith]

Problem:
When the browser language is "pt-br", the app generates a lowercase locale string,
but translation files use uppercase region codes ("pt-BR"). On case-sensitive
systems this causes the file not found error.

Solution:
Normalize locale format so region codes are always uppercase.

Testing:

• Verified Portuguese translations load correctly.
• Verified other locales remain unaffected.

[mister-roboto]

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[petschki]

Thanks for contributing. Please read the instructions for signing the contributor agreement. Also please note, that we're using an old and patched select2 package from here https://github.com/ivaynberg/select2/tree/develop/src/js/select2/i18n ... I'd suggest to check the combined codes and apply the uppercase factory only for the needed ones.

[petschki]

deprecated by #1531