fix: remove excessive bottom padding below input bar on mobile

- Remove dead bottom-[4.5rem] mobile offset on the fixed input bar wrapper
  in page.tsx. The input bar is fixed to inset-x-0 bottom-0 unconditionally
  now, eliminating an unnecessary conditional className via cn().
- Reduce mobile scroll content bottom padding from pb-32 to pb-20 in
  dashboard-view.tsx so content doesn't sit too far above the input bar.

apps/web/app/(app)/page.tsx

@@ -698,12 +698,7 @@ export default function NewPage() {
 				</AnimatePresence>
 
 				{isDashboardShell && (
-					<div
-						className={cn(
-							"pointer-events-none fixed inset-x-0 z-30 bg-gradient-to-t from-black via-black/40 to-transparent pt-12",
-							isMobile ? "bottom-[4.5rem]" : "bottom-0",
-						)}
-					>
+					<div className="pointer-events-none fixed inset-x-0 bottom-0 z-30 bg-gradient-to-t from-black via-black/40 to-transparent pt-12">
 						<div className="pointer-events-auto">
 							<HomeChatComposer onStartChat={handleHomeChatStart} />
 						</div>

apps/web/components/dashboard-view.tsx

@@ -697,7 +697,7 @@ export function DashboardView({
 	return (
 		<div
 			className={cn(
-				"min-h-0 flex-1 overflow-y-auto p-4 pt-2! pb-32 md:p-6 md:pb-36 md:pr-0",
+				"min-h-0 flex-1 overflow-y-auto p-4 pt-2! pb-20 md:p-6 md:pb-36 md:pr-0",
 				dmSansClassName(),
 			)}
 		>