perf: batch-load app status history server-side to eliminate N+1 requests

- Load all app sparkline history in a single server query
- Pass preloadedHistory to AppCard to skip client-side fetch
- Polish empty state with icon, hint text, and add button

src/lib/components/app/AppCard.svelte

@@ -20,18 +20,26 @@
 		checkedAt: string;
 	}
 
-	interface Props {
-		app: AppWithStatus;
+	interface PreloadedHistory {
+		history: StatusPoint[];
+		uptimePercent: number;
 	}
 
-	let { app }: Props = $props();
+	interface Props {
+		app: AppWithStatus;
+		preloadedHistory?: PreloadedHistory | null;
+	}
 
-	let historyData: StatusPoint[] = $state([]);
-	let uptimePercent: number | null = $state(null);
-	let historyLoading = $state(true);
+	let { app, preloadedHistory = null }: Props = $props();
+
+	let historyData: StatusPoint[] = $state(preloadedHistory?.history ?? []);
+	let uptimePercent: number | null = $state(preloadedHistory?.uptimePercent ?? null);
+	let historyLoading = $state(!preloadedHistory);
 
 	const currentStatus = $derived(app.statuses?.[0]?.status ?? 'unknown');
 
+	// Only fetch client-side if no preloaded data was provided
+	if (!preloadedHistory) {
 		onMount(async () => {
 			try {
 				const res = await fetch(`/api/apps/${app.id}/history`);
@@ -48,6 +56,7 @@
 				historyLoading = false;
 			}
 		});
+	}
 
 	const iconDisplay = $derived.by(() => {
 		if (!app.icon) return null;

src/routes/apps/+page.server.ts

@@ -18,7 +18,21 @@ export const load: PageServerLoad = async (event) => {
 		superValidate(zod(createAppSchema))
 	]);
 
-	return { apps, categories, form };
+	// Batch-load sparkline history for all apps (single query instead of N+1)
+	const appIds = apps.map((a) => a.id);
+	const historyMap = appIds.length > 0
+		? await appService.getBatchStatusHistory(appIds)
+		: new Map();
+
+	const appHistories: Record<string, { history: { status: string; responseTime: number | null; checkedAt: string }[]; uptimePercent: number }> = {};
+	for (const [appId, data] of historyMap) {
+		appHistories[appId] = {
+			history: data.history.map((h: { status: string; responseTime: number | null; checkedAt: Date }) => ({ ...h, checkedAt: h.checkedAt.toISOString() })),
+			uptimePercent: data.uptimePercent
+		};
+	}
+
+	return { apps, categories, form, appHistories };
 };
 
 export const actions: Actions = {

src/routes/apps/+page.svelte

@@ -69,9 +69,10 @@
 		{/if}
 
 		{#if data.apps.length === 0}
-			<div class="flex flex-col items-center justify-center rounded-xl border border-border bg-card/50 py-16 text-muted-foreground">
+			<div class="flex flex-col items-center rounded-xl border border-dashed border-border bg-card/30 px-6 py-16 text-center">
+				<div class="mb-4 flex h-16 w-16 items-center justify-center rounded-2xl bg-primary/10">
 					<svg
-					class="mb-3 h-12 w-12 text-muted-foreground/40"
+						class="h-8 w-8 text-primary"
 						xmlns="http://www.w3.org/2000/svg"
 						viewBox="0 0 24 24"
 						fill="none"
@@ -81,16 +82,28 @@
 						stroke-linejoin="round"
 					>
 						<circle cx="12" cy="12" r="10" />
-					<line x1="12" y1="8" x2="12" y2="12" />
-					<line x1="12" y1="16" x2="12.01" y2="16" />
+						<line x1="2" y1="12" x2="22" y2="12" />
+						<path d="M12 2a15.3 15.3 0 0 1 4 10 15.3 15.3 0 0 1-4 10 15.3 15.3 0 0 1-4-10 15.3 15.3 0 0 1 4-10z" />
 					</svg>
-				<p class="text-lg">{$t('app.no_apps')}</p>
-				<p class="mt-1 text-sm">{$t('app.no_apps_hint')}</p>
+				</div>
+				<p class="text-lg font-medium text-foreground">{$t('app.no_apps')}</p>
+				<p class="mt-1 max-w-sm text-sm text-muted-foreground">{$t('app.no_apps_hint')}</p>
+				<button
+					type="button"
+					onclick={() => (showForm = true)}
+					class="mt-4 inline-flex items-center gap-2 rounded-lg bg-primary px-4 py-2 text-sm font-medium text-primary-foreground transition-colors hover:bg-primary/90"
+				>
+					<svg class="h-4 w-4" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+						<line x1="12" y1="5" x2="12" y2="19" />
+						<line x1="5" y1="12" x2="19" y2="12" />
+					</svg>
+					{$t('app.add')}
+				</button>
 			</div>
 		{:else}
 			<div class="grid grid-cols-1 gap-4 sm:grid-cols-2 md:grid-cols-3 lg:grid-cols-4">
 				{#each data.apps as app (app.id)}
-					<AppCard {app} />
+					<AppCard {app} preloadedHistory={data.appHistories[app.id] ?? null} />
 				{/each}
 			</div>
 		{/if}