stats: /stats overview, economy, energy and Gouda pages; CBS series map; nav, homepage, /start and sitemap links

- CBS_SERIES: CPI, household tariffs (2007-now), energy balance, renewables, heat pumps,
  solar, cars, population (monthly, since 1942, components), house prices, housing stock,
  municipal levies for Gouda and its neighbours
- shared StatChart/Kpi/chart helpers with per-chart source attribution
- drop Eurostat nrg_pc_20x_h (404; CBS covers that history)

src/routes/start/+page.svelte

@@ -47,6 +47,12 @@
 		{ name: 'Weigh-in', href: '/trackers/health#body' },
 		{ name: 'DB', href: '/lists/db' }
 	];
+	const statsHits = [
+		{ name: 'Stats', href: '/stats' },
+		{ name: 'Stats: economy', href: '/stats/economy' },
+		{ name: 'Stats: energy', href: '/stats/energy' },
+		{ name: 'Stats: Gouda', href: '/stats/gouda' }
+	];
 
 	const host = $derived(data.host);
 
@@ -328,7 +334,8 @@
 		...trackers
 			.flatMap((t) => [t, ...(t.children ?? [])])
 			.map((t) => ({ name: t.name, href: t.href, kind: 'tracker' })),
-		...extraHits.map((t) => ({ ...t, kind: 'tracker' }))
+		...extraHits.map((t) => ({ ...t, kind: 'tracker' })),
+		...statsHits.map((t) => ({ ...t, kind: 'stats' }))
 	]);
 	const hits = $derived.by(() => {
 		const q = query.trim().toLowerCase();
@@ -559,6 +566,7 @@
 					>{servicesDown.length ? `${servicesDown.length} down` : 'all up'}</span
 				>
 			{/if}
+			<a class="chip" href="/stats" title="Economy, energy and Gouda statistics">stats</a>
 			{#if data.weight}<a class="chip" href="/trackers/health#body" title={data.weight.date}
 					>{data.weight.kg} kg</a
 				>{/if}