Translate new zh_CN and ja UI strings

Fill in Simplified Chinese and Japanese translations for the 186 previously-unfinished entries in each catalog (dashboard/stickers, notebook open/clone, sync info and errors, export dialog, editor/sync preference pages, read-only notebook strings). Verified: valid XML, lrelease reports 1867 finished / 0 unfinished per file, placeholders preserved.

Author: tamlok