feat(i18n): add Korean (ko) locale

[hyun-archisketch]

Adds a Korean (ko) locale, so Korean-speaking users get the Rill UI in Korean (auto-selected from the browser's preferred language in Rill Developer, or via the language switcher).

This picks up #9669, which was closed by its author after the last round of review (only the prettier fix was outstanding). The translation is reused from that PR (Apache-2.0, credited via Co-authored-by) and brought up to date with current main.

Changes

• messages/ko.json: full catalog matching en.json key-for-key and in the same order (2,148 keys, including the plural variants).
  • Compared with feat(i18n): add Korean (ko) locale #9669: translated the 112 keys added since then, retranslated settings_hibernate_confirm_description (its English source changed), and dropped 4 keys that no longer exist in en.json.
  • Terminology follows the existing feat(i18n): add Korean (ko) locale #9669 choices (e.g. measure → 측정값, canvas → 캔버스, bookmark → 북마크).
• project.inlang/settings.json: register ko.
• LanguageSwitcher.svelte + language_ko in en.json / es.json: add the 한국어 option.

Verification

• Every key in en.json exists in ko.json with the same value type, and the {placeholder} names match for all keys (checked with a script).
• npx @inlang/paraglide-js@2.10.0 compile --project web-common/src/lib/i18n/project.inlang succeeds; the generated runtime lists ["en", "es", "ko"].
• prettier@3.5.3 --check passes for the changed JSON files.
• Did not run the app or the vitest suite locally.

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!