feat: info icon on all PageHeader pages + Call Desk header restyled

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/pages/all-leads.tsx

@@ -246,6 +246,7 @@ export const AllLeadsPage = () => {
             <PageHeader
                 title="All Leads"
                 subtitle={`${total} total`}
+                infoText="Campaign-sourced marketing leads. Organic callers are on the Contacts page."
                 controls={
                     <>
                         <div className="w-56">