Root cause: dashboard tabs rendered via t() template literals had no
data-i18n attributes, so setLocale() _applyDOM() could not re-translate
them live. User switching to English in profile saw no effect without
page reload.
Changes:
- i18n.js: expose t/initI18n/setLocale/getLocale/tr globally (window.*)
for non-module script compatibility
- viewer.js: add data-i18n attributes to all 4 dashboard tabs + loading
text + empty state messages (12 elements total)
Verified: tabs show 'Statistics/Bookmarks/Recent/Shared' in EN mode