Add live stats page with metrics sampling and route split

- New sandbox_metrics_snapshots table sampled every 10s (60-day retention)
- Background MetricsSampler goroutine wired into control plane startup
- GET /v1/sandboxes/stats?range=5m|1h|6h|24h|30d endpoint with adaptive
  polling intervals; reserved CPU/RAM uses ceil(paused/2) formula
- StatsPanel component: 4 stat cards + 2 Chart.js line charts (straight
  lines, integer y-axis for running count, dual-axis for CPU/RAM)
- Range filter persisted in URL query param; polls update data silently
  (no blink — loading state only shown on initial mount)
- Split /dashboard/capsules into /list and /stats sub-routes with shared
  layout; capsuleRunningCount store syncs badge across routes
- CreateCapsuleDialog extracted as reusable component

frontend/src/routes/dashboard/capsules/+layout.svelte

@@ -0,0 +1,102 @@
+<script lang="ts">
+	import Sidebar from '$lib/components/Sidebar.svelte';
+	import { capsuleRunningCount } from '$lib/capsule-store.svelte';
+	import { page } from '$app/stores';
+
+	let { children } = $props();
+
+	let collapsed = $state(
+		typeof window !== 'undefined'
+			? localStorage.getItem('wrenn_sidebar_collapsed') === 'true'
+			: false
+	);
+
+	let activeTab = $derived(
+		$page.url.pathname.startsWith('/dashboard/capsules/stats') ? 'stats' : 'list'
+	);
+</script>
+
+<svelte:head>
+	<title>Wrenn — Capsules</title>
+</svelte:head>
+
+<div class="flex h-screen overflow-hidden">
+	<Sidebar bind:collapsed />
+
+	<div class="flex flex-1 flex-col overflow-hidden">
+		<main class="flex-1 overflow-y-auto bg-[var(--color-bg-0)]">
+			<!-- Header area -->
+			<div class="px-7 pt-8">
+				<!-- Top row: title + status chip -->
+				<div class="flex items-center justify-between">
+					<div>
+						<h1 class="font-serif text-page tracking-[-0.02em] text-[var(--color-text-bright)]">
+							Capsules
+						</h1>
+						<p class="mt-2 text-ui text-[var(--color-text-secondary)]">
+							Isolated VMs. Start cold in under a second — pause, snapshot, or destroy at will.
+						</p>
+					</div>
+
+					<div class="flex items-center gap-3">
+						<!-- Status chip -->
+						<div
+							class="flex items-center gap-2.5 rounded-[var(--radius-card)] border border-[var(--color-accent)]/20 bg-[var(--color-bg-2)] px-3.5 py-2"
+						>
+							<span class="relative flex h-[8px] w-[8px]">
+								<span
+									class="animate-status-ping absolute inline-flex h-full w-full rounded-full bg-[var(--color-accent)]"
+								></span>
+								<span class="relative inline-flex h-[8px] w-[8px] rounded-full bg-[var(--color-accent)]"></span>
+							</span>
+							<span class="font-mono text-body font-semibold text-[var(--color-accent-bright)]">{capsuleRunningCount.value}</span>
+							<span class="text-ui text-[var(--color-text-secondary)]">running now</span>
+						</div>
+					</div>
+				</div>
+
+				<!-- Tab bar -->
+				<div class="mt-5 flex gap-1 border-b border-[var(--color-border)]">
+					<a
+						href="/dashboard/capsules/list"
+						class="flex items-center gap-2 border-b-2 px-4 py-2.5 text-ui font-medium transition-colors duration-150 {activeTab === 'list'
+							? 'border-[var(--color-accent)] text-[var(--color-accent-bright)]'
+							: 'border-transparent text-[var(--color-text-secondary)] hover:text-[var(--color-text-primary)]'}"
+					>
+						<svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+							<line x1="8" y1="6" x2="21" y2="6" /><line x1="8" y1="12" x2="21" y2="12" /><line x1="8" y1="18" x2="21" y2="18" />
+							<line x1="3" y1="6" x2="3.01" y2="6" /><line x1="3" y1="12" x2="3.01" y2="12" /><line x1="3" y1="18" x2="3.01" y2="18" />
+						</svg>
+						List
+					</a>
+					<a
+						href="/dashboard/capsules/stats"
+						class="flex items-center gap-2 border-b-2 px-4 py-2.5 text-ui font-medium transition-colors duration-150 {activeTab === 'stats'
+							? 'border-[var(--color-accent)] text-[var(--color-accent-bright)]'
+							: 'border-transparent text-[var(--color-text-secondary)] hover:text-[var(--color-text-primary)]'}"
+					>
+						<svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+							<polyline points="22 12 18 12 15 21 9 3 6 12 2 12" />
+						</svg>
+						Stats
+					</a>
+				</div>
+			</div>
+
+			{@render children()}
+		</main>
+
+		<!-- Status bar -->
+		<footer
+			class="flex h-7 shrink-0 items-center justify-end border-t border-[var(--color-border)] bg-[var(--color-bg-1)] px-7"
+		>
+			<div class="flex items-center gap-1.5">
+				<span class="relative flex h-[5px] w-[5px]">
+					<span class="animate-status-ping absolute inline-flex h-full w-full rounded-full bg-[var(--color-accent)]"></span>
+					<span class="relative inline-flex h-[5px] w-[5px] rounded-full bg-[var(--color-accent)]"></span>
+				</span>
+				<span class="font-mono text-label uppercase tracking-[0.04em] text-[var(--color-text-secondary)]">All systems operational</span>
+			</div>
+		</footer>
+	</div>
+</div>