feat: add Korean (한국어) localization

[soohanpark]

Summary

Adds native Korean (ko) as a first-class language, integrated into CodexBar's existing localization system.

• ko.lproj/Localizable.strings — all 1,040 strings translated into native, idiomatic macOS-style Korean (Apple-standard terminology: 설정, 새로 고침, 종료, 메뉴 막대, 할당량, 크레딧 구매…). Format specifiers (%@, %lld, %1$@…) and \(name) interpolation placeholders are preserved exactly; positional specifiers are used where Korean word order requires reordering.
• Registered ko in the AppLanguage enum + Settings → Language picker.
• Added the localized "language_korean" name to every existing catalog (e.g. en→"Korean", ja→"韓国語", zh-Hans→"韩语") so the picker renders correctly in all languages.
• Extended LocalizationLanguageCatalogTests parity list.

No changes were needed to Localization.swift (its default case already maps "ko" → Locale("ko")) or Package.swift (.process("Resources") auto-bundles the new catalog).

Using it

Selectable as 한국어 in Settings → Language (requires app restart). In the default System mode it is now picked up automatically for users whose macOS language is Korean.

Verification

• ✅ Deterministic parity gate (plutil + checks): 1040/1040 keys match en, 0 missing/extra, 0 placeholder/format-specifier mismatches.
• ✅ swift build succeeds.
• ✅ All 19 localization tests pass (catalog parity, bundle resolution, no-raw-English coverage, popup, status-menu refresh).
• ✅ Full suite (3781 tests): the only 2 failures are pre-existing and unrelated to this change (a flaky main-thread-watchdog timing test, and a MenuCardModelTests date assertion that hard-codes an English date while subscriptionDateString uses Locale.current — both reproduce on main with these changes stashed).

🤖 Generated with Claude Code

[soohanpark]

Superseded by upstream PR steipete#1460 (targeting the original repo).