feat(phase3): import/export, sparklines, user theme overrides

- JSON import/export with conflict resolution (skip/overwrite) + admin UI
- Ping history sparklines on AppWidget and AppCard (24h, 288 points)
- Hourly cleanup job for old AppStatus records
- User theme preferences (hue, saturation, mode, background, locale)
- Settings page with ThemeCustomizer (sliders, toggles, live preview)
- Prisma migration for user preference fields
- i18n translations for all new strings (EN/RU)

src/lib/components/app/AppCard.svelte

@@ -1,5 +1,8 @@
 <script lang="ts">
+	import { t } from 'svelte-i18n';
+	import { onMount } from 'svelte';
 	import AppHealthBadge from './AppHealthBadge.svelte';
+	import SparklineChart from './SparklineChart.svelte';
 
 	interface AppWithStatus {
 		id: string;
@@ -12,14 +15,40 @@
 		statuses: Array<{ status: string; responseTime: number | null; checkedAt: string | Date }>;
 	}
 
+	interface StatusPoint {
+		status: string;
+		checkedAt: string;
+	}
+
 	interface Props {
 		app: AppWithStatus;
 	}
 
 	let { app }: Props = $props();
 
+	let historyData: StatusPoint[] = $state([]);
+	let uptimePercent: number | null = $state(null);
+	let historyLoading = $state(true);
+
 	const currentStatus = $derived(app.statuses?.[0]?.status ?? 'unknown');
 
+	onMount(async () => {
+		try {
+			const res = await fetch(`/api/apps/${app.id}/history`);
+			if (res.ok) {
+				const json = await res.json();
+				if (json.success && json.data) {
+					historyData = json.data.history ?? [];
+					uptimePercent = json.data.uptimePercent ?? null;
+				}
+			}
+		} catch {
+			// Silently fail — sparkline is non-critical
+		} finally {
+			historyLoading = false;
+		}
+	});
+
 	const iconDisplay = $derived.by(() => {
 		if (!app.icon) return null;
 
@@ -75,6 +104,18 @@
 		<p class="mt-1 line-clamp-2 text-xs text-muted-foreground">{app.description}</p>
 	{/if}
 
+	<!-- Sparkline -->
+	{#if historyLoading}
+		<div class="mt-2 h-5 w-20 animate-pulse rounded bg-muted"></div>
+	{:else if historyData.length > 0}
+		<div class="mt-2 flex items-center gap-1.5">
+			<SparklineChart data={historyData} />
+			{#if uptimePercent !== null}
+				<span class="text-[10px] text-muted-foreground">{uptimePercent}% {$t('app.uptime')}</span>
+			{/if}
+		</div>
+	{/if}
+
 	{#if app.category}
 		<span
 			class="mt-2 inline-block self-start rounded-full bg-muted px-2 py-0.5 text-xs text-muted-foreground"