perf: batch-load app history to eliminate N+1 fetches on board load

Previously each AppWidget fetched /api/apps/{id}/history individually
on mount, causing N sequential HTTP requests. Now the board page
server load fetches all app histories in a single Prisma query via
getBatchStatusHistory() and passes them to AppWidget via Svelte
context. AppWidget uses the pre-loaded data immediately with a
fallback fetch for non-board contexts.

src/lib/components/widget/AppWidget.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { onMount } from 'svelte';
+	import { onMount, getContext } from 'svelte';
 	import AppHealthBadge from '$lib/components/app/AppHealthBadge.svelte';
 	import AnimatedStatusRing from '$lib/components/app/AnimatedStatusRing.svelte';
 	import SparklineChart from '$lib/components/app/SparklineChart.svelte';
@@ -48,9 +48,13 @@
 
 	const cardStyleClass = $derived(`card-${theme.cardStyle}`);
 
-	let historyData: StatusPoint[] = $state([]);
-	let uptimePercent: number | null = $state(null);
-	let historyLoading = $state(true);
+	// Use pre-loaded history from context (set by board page) to avoid N+1 fetches
+	const appHistories = getContext<Record<string, { history: StatusPoint[]; uptimePercent: number }> | undefined>('appHistories');
+	const preloaded = appHistories?.[app.id];
+
+	let historyData: StatusPoint[] = $state(preloaded?.history ?? []);
+	let uptimePercent: number | null = $state(preloaded?.uptimePercent ?? null);
+	let historyLoading = $state(!preloaded);
 	let linksExpanded = $state(false);
 	let showContextMenu = $state(false);
 	let contextMenuPos = $state({ x: 0, y: 0 });
@@ -74,7 +78,9 @@
 		}
 	});
 
+	// Fallback: fetch history only if not pre-loaded via context
 	onMount(async () => {
+		if (preloaded) return;
 		try {
 			const res = await fetch(`/api/apps/${app.id}/history`);
 			if (res.ok) {