preserving navigation

site/src/components/ActivityFeed.svelte

@@ -34,6 +34,7 @@
   let shown = PAGE_SIZE;
   let loading = true;
   let error = '';
+  let mounted = false;
 
   $: filtered = sport === 'all' ? all : all.filter(a => a.sport === sport);
   $: visible = filtered.slice(0, shown);
@@ -41,7 +42,16 @@
 
   $: if (sport) shown = PAGE_SIZE; // reset pagination on filter change
 
+  $: if (mounted) {
+    const params = new URLSearchParams(window.location.search);
+    if (sport === 'all') params.delete('sport'); else params.set('sport', sport);
+    const qs = params.toString();
+    history.replaceState(null, '', qs ? `?${qs}` : window.location.pathname);
+  }
+
   onMount(async () => {
+    sport = (new URLSearchParams(window.location.search).get('sport') as Sport | 'all') ?? 'all';
+    mounted = true;
     try {
       const res = await fetch(`${import.meta.env.BASE_URL}data/index.json`);
       if (!res.ok) throw new Error(`HTTP ${res.status}`);