Register Khmer (km) locale, add complete 1,394-entry dashboard translation,
and show the Cambodia flag in the language selector. Place Khmer immediately
before Thai in the selector and keep the header locale in sync after switching.
Move shutdown into header popup + profile, move remote into sidebar above
settings, add flag-only language switcher in header, and add language card
plus shutdown/logout actions to the profile page.
Co-authored-by: Cursor <cursoragent@cursor.com>