fix(redesign): align topbar horizontal padding with page content

Topbar wrapper used md:px-0 (edge-to-edge of main column) while the
page content wrapper used md:px-8 (32px side padding). Result was a
32px overshoot on each side of the topbar pill versus the hero, stat
cards, and panels below it.

Match the wrappers — topbar now uses md:px-8 too. Left/right edges of
the search bar pill line up with the hero/stat panels.

frontend/src/routes/+layout.svelte

@@ -607,7 +607,7 @@
 			style="padding-bottom: calc(4rem + env(safe-area-inset-bottom, 0px));">
 
 			<!-- Always-visible topbar — search + utilities + primary CTA -->
-			<div class="topbar px-4 md:px-8 pt-4 md:pt-6">
+			<div class="topbar px-4 md:px-8">
 				<div class="topbar-glass">
 					<button type="button" class="topbar-search" onclick={() => openSearch?.()}>
 						<NavIcon name="mdiMagnify" size={16} />