Fix admin i18n sync coverage

[mylukin]

Summary

• sync admin i18n keys from the root command
• translate request-detail lazy payload copy across zh-hans, zh-hant, ja, and ko
• stop forcing rules/eval/fallback back to English during i18n sync
• add request-detail locale coverage guard

Verification

• pnpm i18n:sync
• locale audit: zh-hans/zh-hant/ja/ko same=0 missing=0 extra=0
• pnpm exec vitest run apps/admin/src/lib/i18n/nav-locales.test.ts apps/admin/src/lib/i18n/settings-locales.test.ts apps/admin/src/lib/i18n/providers-locales.test.ts apps/admin/src/lib/i18n/dashboard-locales.test.ts apps/admin/src/lib/i18n/mcp-locales.test.ts apps/admin/src/lib/i18n/attempt-code-locales.test.ts apps/admin/src/lib/i18n/request-detail-locales.test.ts apps/admin/src/lib/components/CreateKeyDialog.test.ts apps/admin/src/routes/keys/keys.test.ts apps/admin/src/routes/requests/requests.test.ts
• pnpm lint
• pnpm typecheck
• pnpm build
• git diff --check