ActivityFeed: add title search bar with URL sync

site/src/components/ActivityFeed.svelte

@@ -42,6 +42,7 @@
   let datePre = 'all';
   let dateFrom = '';
   let dateTo = '';
+  let query = '';
   let shown = PAGE_SIZE;
   let loading = true;
   let loadingMore = false;
@@ -87,8 +88,11 @@
     (!dateFrom || a.started_at >= dateFrom) && (!dateTo || a.started_at < dateTo)
   );
   $: filtered = sport === 'all' ? withDate : withDate.filter(a => a.sport === sport);
-  $: visible = filtered.slice(0, shown);
-  $: canShowMore = shown < filtered.length;
+  $: withSearch = query.trim()
+    ? filtered.filter(a => a.title?.toLowerCase().includes(query.trim().toLowerCase()))
+    : filtered;
+  $: visible = withSearch.slice(0, shown);
+  $: canShowMore = shown < withSearch.length;
   $: hasMore = canShowMore || pendingShards.length > 0 || feedNextPage > 0;
 
   async function loadMore() {
@@ -122,12 +126,13 @@
     }
   }
 
-  $: if (sport || datePre) shown = PAGE_SIZE; // reset pagination on filter change
+  $: if (sport || datePre || query) shown = PAGE_SIZE; // reset pagination on filter change
 
   $: if (mounted) {
     const params = new URLSearchParams(window.location.search);
     if (sport === 'all') params.delete('sport'); else params.set('sport', sport);
     if (datePre === 'all') params.delete('date'); else params.set('date', datePre);
+    if (!query.trim()) params.delete('q'); else params.set('q', query.trim());
     const qs = params.toString();
     history.replaceState(null, '', qs ? `?${qs}` : window.location.pathname);
   }
@@ -136,6 +141,7 @@
     const params = new URLSearchParams(window.location.search);
     sport   = (params.get('sport') as Sport | 'all') ?? 'all';
     datePre = params.get('date') ?? 'all';
+    query   = params.get('q') ?? '';
     mounted = true;
 
     // Resolve the logged-in handle so we can show the owner their private activities.
@@ -204,15 +210,25 @@
   {/each}
   {#if all.length > 0}
     <span class="ml-auto text-sm text-zinc-500 self-center">
-      {#if totalActivities > filtered.length}
-        {filtered.length} of {totalActivities} activities
+      {#if totalActivities > withSearch.length}
+        {withSearch.length} of {totalActivities} activities
       {:else}
-        {filtered.length} {filtered.length === 1 ? 'activity' : 'activities'}
+        {withSearch.length} {withSearch.length === 1 ? 'activity' : 'activities'}
       {/if}
     </span>
   {/if}
 </div>
 
+<!-- Search -->
+<div class="relative mb-3">
+  <input
+    type="search"
+    placeholder="Search activities…"
+    bind:value={query}
+    class="w-full px-4 py-2 rounded-lg bg-zinc-900 border border-zinc-700 text-white placeholder-zinc-500 text-sm focus:outline-none focus:border-zinc-500 transition-colors"
+  />
+</div>
+
 <!-- Date filter bar -->
 <div class="flex gap-2 mb-6 flex-wrap">
   {#each [{ value: 'all', label: 'All time' }, { value: '7d', label: '7 days' }, { value: '30d', label: '30 days' }, { value: '6mo', label: '6 months' }, ...allYears.map(y => ({ value: y, label: y }))] as d}
@@ -238,8 +254,10 @@
   </div>
 {:else if error}
   <p class="text-red-400 text-center py-12">Could not load activities: {error}</p>
-{:else if filtered.length === 0}
-  <p class="text-zinc-500 text-center py-12">No activities found.</p>
+{:else if withSearch.length === 0}
+  <p class="text-zinc-500 text-center py-12">
+    {#if query.trim()}No activities match "{query.trim()}".{:else}No activities found.{/if}
+  </p>
 {:else}
   <div class="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4">
     {#each visible as a (a.id)}