trackers: group cars, trains, planes and wildlife under one spotting tracker with /trackers/spotting landing page and category switcher

src/routes/trackers/cars/+layout.svelte

@@ -0,0 +1,8 @@
+<script lang="ts">
+	import SpottingSwitcher from '#lib/components/SpottingSwitcher.svelte';
+
+	let { children } = $props();
+</script>
+
+<SpottingSwitcher />
+{@render children()}