Podcast tab: show podcast.necloud.us inside the app

Audio and Podcast now share kept-alive frames that stay loaded while hidden.
A plain-http address still falls back to a launcher (a secure page cannot
frame http content).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

public/style.css

@@ -229,3 +229,6 @@ textarea { padding: 12px 14px; resize: vertical; font-family: inherit; }
 .chk { display: flex; align-items: center; gap: 10px; color: var(--text); font-size: 16px; margin: 14px 0 0; }
 .chk input { width: 22px; height: 22px; }
 .row input[type=checkbox] { width: 22px; height: 22px; }
+
+/* Several kept-alive frames share #audiowrap; only the active one is shown (the others stay loaded, out of sight) */
+#audiowrap iframe:not(.act) { position: absolute; width: 1px; height: 1px; opacity: 0; pointer-events: none; border: 0; }