Nas margens do emprego, no centro da pandemia: experiências de desproteção e vulnerabilidade social no Grande Confinamento*On the Margins of Employment, in the Centre of the Pandemic: Experiences of Unprotection and Social Vulnerability in the Great LockdownEn marge de l?emploi, au centre de la pandémie: expériences de non-protection et de vulnérabilité sociale durant le Grand Confinemen