feat(web): favicon + toast feedback (polish)

Add a vinyl-record favicon (icon.svg) — fixes the favicon.ico 404 console
error. Lightweight toast system (ToastHost + toast()) fired on request, wanted
add, search, follow, and want actions so submits give explicit feedback.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/app/wanted/wanted-client.tsx

@@ -5,6 +5,7 @@ import { PageHead } from "../_ui/page-head";
 import { SectionHeader } from "../_ui/section-header";
 import { CoverArt } from "../_ui/cover-art";
 import { AlbumModal } from "../_ui/album-modal";
+import { toast } from "../_ui/toast";
 
 type Wanted = {
   id: string;
@@ -51,6 +52,7 @@ export function WantedClient() {
       setError((await res.json()).error ?? "Couldn’t add that — no MusicBrainz match?");
       return;
     }
+    toast("Added to wanted");
     setArtist("");
     setAlbum("");
     refresh();
@@ -58,6 +60,7 @@ export function WantedClient() {
 
   async function searchNow(w: Wanted) {
     await fetch(`/api/releases/${w.id}/search`, { method: "POST" });
+    toast(`Searching for ${w.album}`);
     refresh();
   }