feat(web): propagate YouTube brand icon to the lobby track submission

- "Ajouter" button shows the SiYoutube logo
- each submitted track card gets a YouTube open link (verify the pasted song)

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

apps/web/src/components/lobby-view.tsx

@@ -11,6 +11,7 @@ import {
   Trash2,
   type LucideIcon,
 } from "lucide-react"
+import { SiYoutube } from "@icons-pack/react-simple-icons"
 import type {
   BlindtestMode,
   GameType,
@@ -361,6 +362,16 @@ function TrackSubmission({
                 className="h-10 w-16 shrink-0 rounded object-cover"
               />
               <span className="line-clamp-2 flex-1 text-xs">{t.title}</span>
+              <a
+                href={`https://www.youtube.com/watch?v=${t.youtubeId}`}
+                target="_blank"
+                rel="noreferrer"
+                title="Ouvrir sur YouTube"
+              >
+                <Button size="icon-sm" variant="secondary">
+                  <SiYoutube color="default" />
+                </Button>
+              </a>
               <Button
                 size="icon-sm"
                 variant="secondary"
@@ -389,7 +400,7 @@ function TrackSubmission({
             disabled={submitting || !url.trim()}
             onClick={submit}
           >
-            Ajouter
+            <SiYoutube color="default" /> Ajouter
           </Button>
         </div>
       )}