Add i18n Support

[google-labs-jules]

This change adds internationalization support to the application, translating all existing English strings into French, German, Italian, Ukrainian, and Hindi. It introduces the vue-i18n library, creates locale files for each language, and replaces all hardcoded strings with i18n keys. A language switcher has been added to allow users to select their preferred language. All outstanding issues from the code review have been addressed.

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PR created automatically by Jules for task 7706765492570360763 started by @loleg

[google-labs-jules]

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