i18n: add Korean (ko) locale

[leestana01]

Proposal

I'd like to contribute Korean (ko) translations for all 41 calendar-related locale keys.

A branch with the complete implementation is ready at leestana01:i18n/add-korean-locale. The repository restricts PRs to collaborators, so I'm opening this discussion first.

Changes

• resources/locales/i18n.yml — 41 new ko: entries across all existing keys
• crates/common/src/i18n.rs — add "ko" to calendar_templates_include_minutes test

Translation notes

• Date format templates follow Korean conventions: year/month/day ordering (%Y년 %-m월 %-d일) with AM/PM notation (%p).
• Calendar UI terms (organizer, attendees, when, etc.) align with Google Calendar Korean conventions.
• RSVP-related strings use natural Korean phrasing (참석 여부) rather than transliterating "RSVP".
• $name placeholder variables are preserved with appropriate Korean particles (e.g., $name님이).

Happy to adjust anything based on feedback. Let me know if I should submit this differently.

[ardamafzal]

I built a small tool to translate JSON i18n files without breaking placeholders, might be useful here
Would love any feedback
Link - https://localizejson.lovable.app/