Register `ko` in the locale list, language names, and labels, and ship
messages/ko.json so the whole UI — dashboard, settings, share views,
clinician PDF, notifications, and AI prompts — renders in Korean.
Extend the locale-parity, English-leak, plural-completeness, and copy
guard tests to cover the new locale, and update README/CONTRIBUTING to
list Korean among the supported languages.
The client bundle carries only the active locale — resolved on the
server and handed to the provider with no hydration flash, halving the
dashboard route to under a megabyte parsed (288 KiB gzip). The auth
shell renders the app chrome immediately instead of a spinner while the
session resolves in parallel, the widgets request folds into the
snapshot it duplicated, and insight pills prefetch their sub-pages —
a first visit to a sub-page lands in about ninety milliseconds instead
of nearly a second.