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/_ui/artist-modal.tsx

@@ -3,6 +3,7 @@
 import { useEffect, useState } from "react";
 import { Modal } from "./modal";
 import { CoverArt } from "./cover-art";
+import { toast } from "./toast";
 
 type Rel = {
   rgMbid: string;
@@ -61,7 +62,10 @@ export function ArtistModal({
       headers: { "content-type": "application/json" },
       body: JSON.stringify({ mbid, name }),
     });
-    if (res.ok || res.status === 409) setFollowed(true);
+    if (res.ok || res.status === 409) {
+      setFollowed(true);
+      toast(`Following ${name}`);
+    }
   }
 
   async function want(r: Rel) {
@@ -78,7 +82,10 @@ export function ArtistModal({
         firstReleaseDate: r.firstReleaseDate,
       }),
     });
-    if (res.ok) setWanted((s) => new Set(s).add(r.rgMbid));
+    if (res.ok) {
+      setWanted((s) => new Set(s).add(r.rgMbid));
+      toast(`Added ${r.album}`);
+    }
   }
 
   return (