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>

docker-compose.yml

@@ -16,7 +16,7 @@ services:
       ONLYOFFICE_URL: ${ONLYOFFICE_URL:-https://onlyoffice.necloud.us}
       AUDIOBOOKS_URL: ${AUDIOBOOKS_URL:-https://audiobooks.necloud.us}
       VERSE_URL: ${VERSE_URL:-https://versebyversewithnate.us/admin}
-      PODCAST_URL: ${PODCAST_URL:-http://172.16.16.106:8383/}
+      PODCAST_URL: ${PODCAST_URL:-https://podcast.necloud.us/}
       ONLYOFFICE_JWT_SECRET: ${ONLYOFFICE_JWT_SECRET:-}    # same value as the OnlyOffice server's JWT secret
       PUBLIC_URL: ${PUBLIC_URL:-}                           # e.g. https://hub.necloud.us (OnlyOffice posts saved edits here)
       HUB_SETUP_CODE: ${HUB_SETUP_CODE:-}                   # first passkey; if empty, a code is printed in the log