Shift+M enters a kaomoji quick-input mode backed by the kaomoji table in
others.db, supporting full pinyin, abbreviated pinyin, English words, and
shuangpin expansion. Candidates commit directly via the new
CandidateSource::Kaomoji; a [utility] kaomoji_mode toggle is wired through
settings. Hardens candidate payload rendering (HTML / backtick / comma
escaping) so kaomoji, which often contain < > & and commas, display correctly.
