fix: combine stats and search into single centered margin container (#528)

- Stats and search now in one flex container, centered in left margin
- Mirrors how logout is centered in right margin
- Container has max-width to prevent overflow into content area
- Stats can wrap to 2 rows if numbers get large (flex-wrap)
- Smaller font size (0.75rem) for stats to fit better
- Breakpoint at 1599px to account for queue panel

frontend/src/lib/components/Header.svelte

···
 </script>
 
 <header>
-	<!-- Stats and search positioned on far left, splitting margin into thirds -->
-	<div class="stats-left desktop-only">
+	<!-- Stats and search together in left margin, centered as a group -->
+	<div class="margin-left desktop-only">
 		<PlatformStats variant="header" />
-	</div>
-	<div class="search-left desktop-only">
 		<SearchTrigger />
 	</div>
-	<!-- Logout positioned on far right, mirroring stats -->
+	<!-- Logout positioned on far right, centered in right margin -->
 	{#if isAuthenticated}
 		<div class="logout-right desktop-only">
 			<button onclick={onLogout} class="btn-logout-outer" title="log out">logout</button>
···
 		transform: scale(0.94);
 	}
 
-	.stats-left {
-		position: absolute;
-		left: calc((100vw - var(--queue-width, 0px) - 800px) / 6);
-		top: 50%;
-		transform: translate(-50%, -50%);
-		transition: left 0.3s ease;
-	}
-
-	.search-left {
+	.margin-left {
 		position: absolute;
-		left: calc((100vw - var(--queue-width, 0px) - 800px) / 3 + 20px);
+		/* Center in the left margin: halfway between left edge and content area */
+		left: calc((100vw - var(--queue-width, 0px) - 800px) / 4);
 		top: 50%;
 		transform: translate(-50%, -50%);
 		transition: left 0.3s ease;
+		display: flex;
+		align-items: center;
+		gap: 1rem;
+		/* Constrain width to prevent overflow into content area */
+		max-width: calc((100vw - var(--queue-width, 0px) - 800px) / 2 - 2rem);
 	}
 
 	.logout-right {
···
 		color: var(--bg-primary);
 	}
 
-	/* Hide margin-positioned elements and switch to mobile layout at the same breakpoint */
-	@media (max-width: 1399px) {
-		.stats-left,
-		.search-left,
+	/* Hide margin-positioned elements and switch to mobile layout at the same breakpoint.
+	   Account for queue panel (320px) potentially being open - need extra headroom */
+	@media (max-width: 1599px) {
+		.margin-left,
 		.logout-right {
 			display: none !important;
 		}

frontend/src/lib/components/PlatformStats.svelte

···
 	.stats-header {
 		display: flex;
 		align-items: center;
-		gap: 0.75rem;
+		gap: 0.5rem 0.75rem;
+		flex-wrap: wrap;
+		justify-content: center;
+		max-width: 280px;
 	}
 
 	.header-stat {
···
 		align-items: center;
 		gap: 0.3rem;
 		color: var(--text-secondary);
-		font-size: 0.8rem;
+		font-size: 0.75rem;
 		transition: color 0.2s;
+		white-space: nowrap;
 	}
 
 	.header-stat:hover {