feat(web): quick-filter on Library tabs (Tier B5)

Add a debounced QuickFilter input at the top of each Library section
to narrow the loaded list without leaving the tab. Server-side
/search remains the route for full-library searches.

- QuickFilter.svelte: 120ms debounced two-way bound input with a
  clear button and Escape-to-clear.
- Artists: filter by name; empty-match copy includes a "Search the
  full library" link to /search/artists.
- Albums: filter by title + artist_name; same fallback link.
- Liked: filters all three sub-sections (artists/albums/tracks);
  sub-section header hides when its filtered length is zero.
- History: filters flatEvents before groupByDay, so day-grouping
  reflects the filter.
- Playlists: filters owned + public by name; owners CTA stays.

Covered by QuickFilter unit tests (debounce + clear + Escape).

web/src/routes/library/history/+page.svelte

@@ -6,18 +6,33 @@
   import InfiniteScrollSentinel from '$lib/components/InfiniteScrollSentinel.svelte';
   import LibrarySkeleton from '$lib/components/LibrarySkeleton.svelte';
   import ApiErrorBanner from '$lib/components/ApiErrorBanner.svelte';
+  import QuickFilter from '$lib/components/QuickFilter.svelte';
 
   const queryStore = createHistoryQuery();
   const query = $derived($queryStore);
   const flatEvents = $derived(query.data?.pages?.flatMap((p) => p.events) ?? []);
-  const grouped = $derived(groupByDay(flatEvents, new Date()));
+
+  let filter = $state('');
+  const filteredEvents = $derived.by(() => {
+    const q = filter.trim().toLowerCase();
+    if (!q) return flatEvents;
+    return flatEvents.filter((e) =>
+      e.track.title.toLowerCase().includes(q) ||
+      e.track.artist_name.toLowerCase().includes(q) ||
+      (e.track.album_title ?? '').toLowerCase().includes(q)
+    );
+  });
+  const grouped = $derived(groupByDay(filteredEvents, new Date()));
 </script>
 
 <svelte:head><title>{pageTitle('Library · History')}</title></svelte:head>
 
 <div class="space-y-4">
-  <header>
+  <header class="flex flex-wrap items-end justify-between gap-3">
     <h1 class="font-display text-2xl font-medium text-text-primary">History</h1>
+    {#if flatEvents.length > 0}
+      <QuickFilter bind:value={filter} placeholder="Filter history" />
+    {/if}
   </header>
 
   {#if query.isPending}
@@ -26,6 +41,11 @@
     <ApiErrorBanner error={query.error} onRetry={query.refetch} />
   {:else if flatEvents.length === 0}
     <p class="p-8 text-center text-text-secondary">No listening history yet.</p>
+  {:else if filter.trim() && filteredEvents.length === 0}
+    <p class="text-text-secondary">
+      No history in your loaded events matches
+      <span class="font-medium">'{filter.trim()}'</span>.
+    </p>
   {:else}
     {#each grouped as group (group.label)}
       <section>