The bare native file input (browser-chrome "Choose Files" button) clashed
with every other styled field on the screen -- new .m-file-input component
class mirrors management's own .file-input treatment, recolored for the
mobile palette. Also "Linked to {team}" reads clearer than "Posted for
{team}" now that the field is a hard-locked link, not a free-text audience.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>