Add tab icons and fix mobile dashboard styling issues

- Add matching lucide-react icons to tab/mode switcher buttons on
  payments, at-the-door, manual, email-attendees, whatsapp-attendees,
  and admin cashup pages, mirroring icons already used in their help menus
- Fix navbar Logout button sitting lower than other nav links (missing
  border/padding classes that other links use for their active-underline)
- Fix stat card labels getting truncated on mobile by removing the
  ellipsis-cut label and widening the mobile grid to one column
- Fix Revenue trend / Top performing events rendering outside the
  viewport on mobile by containing horizontal overflow and truncating
  long event titles in the table

frontend/src/components/shared/StatCard.tsx

@@ -39,7 +39,7 @@ export function StatCard({
           <Icon className={"w-5 h-5 " + t.icon} />
         </div>
         <div className="min-w-0">
-          <div className="text-xs text-gray-500 truncate">{label}</div>
+          <div className="text-xs text-gray-500 leading-snug">{label}</div>
           <div className="text-xl font-semibold text-gray-900 truncate">{value}</div>
         </div>
       </div>
@@ -67,5 +67,5 @@ export function StatCard({
 }
 
 export function StatCardRow({ children }: { children: React.ReactNode }) {
-  return <div className="grid grid-cols-2 sm:grid-cols-3 lg:grid-cols-5 gap-4">{children}</div>;
+  return <div className="grid grid-cols-1 sm:grid-cols-3 lg:grid-cols-5 gap-4">{children}</div>;
 }