fix: enable professor face attendance and fix upcoming classes weekly logic

fix: make leave emails async to prevent hanging and display success message

feat: group student leave applications by submission date

fix: split global leaves into individual subject leaves and add HF persistent storage support

fix: corrected pending leaves count on professor dashboard

fix: mirrored camera UI and dropdown colors

fix: speed up dlib build with parallel compilation

fix: TiDB compatible schema + Dockerfile fix

fix: remove obsolete libgl1-mesa-glx package

initial commit