Add Korean (ko) locale translation

[daeho-ro]

Summary

Adds a Korean (ko) locale so the theme renders in Korean when the publication language is set to ko. Korean was previously absent from locales/, so Korean-language sites fell back to English UI strings.

Changes

• Add locales/ko.json — a complete Korean translation of all 119 UI strings from locales/en.json.

Approach

Follows the Ghost theme-translations guidelines:

• Copied from en.json — keys are left untouched (they are the {{t}} template lookup strings); only values are translated.
• Placeholders preserved — {authors}, {primaryAuthor}, {numberOfIssues}, {numberOfPosts}, {page}, {totalPages}, {tiers}, {sitetitle}, {ghostlink}, and the % count token are kept verbatim so runtime substitution still works.
• Alphabetical key order preserved (mirrors en.json).
• Example placeholder value localized to match sibling locales (jamie@example.com → hong@example.com).
• Unlike the partially-filled locales (e.g. zh.json), every key is translated — no empty values.

Verification

• Key parity vs en.json: 119/119, no missing, no extra, no empty values.
• pnpm test:ci (gscan --fatal --verbose) passes — no fatal Ghost 6.x compatibility issues.

Notes

To surface Korean on a live site, set Settings → Publication language to ko in Ghost admin.