Smartlist should be reductible to 0

• Actually, minimum smartlist size is 120px. the smartlist should be reductible (and if size = 0, we can pass in responsive mode)

I'd be ok with a non-zero minimum width (then moving to responsive), but narrower than today.

https://review.jami.net/c/jami-client-qt/+/20025

mentioned in issue #667 (closed)

mentioned in commit 7139eecc

closed