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/routes/settings/+page.server.ts

@@ -0,0 +1,28 @@
+import type { PageServerLoad } from './$types.js';
+import { requireAuth } from '$lib/server/middleware/authenticate.js';
+import { prisma } from '$lib/server/prisma.js';
+
+export const load: PageServerLoad = async (event) => {
+	const user = requireAuth(event);
+
+	const dbUser = await prisma.user.findUnique({
+		where: { id: user.id },
+		select: {
+			themeMode: true,
+			primaryHue: true,
+			primarySaturation: true,
+			backgroundType: true,
+			locale: true
+		}
+	});
+
+	return {
+		preferences: dbUser ?? {
+			themeMode: null,
+			primaryHue: null,
+			primarySaturation: null,
+			backgroundType: null,
+			locale: null
+		}
+	};
+};