make disclaimer about shift sponsorship/endorsement of calendar rides more obvious

Per the email thread on the board of directors group, based on community confusion that shift was somehow "sponsoring" or "endorsing" rides on our calendar. While proposal is to move or duplicate the existing end-of-list disclaimer, to the top, it might also be useful see if we can find a non-annoying way to link to the existing mission statement + code of conduct pages in the statement to show that it's more nuanced than "we don't run these rides"?