Firefox preloads the audio file in embedded player

Describe the bug

The audio player on the embed page for an episode preloads the audio file in the Firefox browser. This presumably will create false positives for download analytics.

Steps to reproduce

1. Visit the embed URL of any episode with Firefox
2. Note the progress bar of the player shows the file is being downloaded
3. Compare e.g. Chromium - the download progress bar doesn't continue until the user presses play.

Expected behavior

No download request is made until the user explicitly interacts with the player.

(It seems the spec doesn't require honouring the 'preload' attribute (see <audio> element on MDN), but a test of a plain <audio> tag shows that Firefox usually does.)

Actual behavior

Firefox ignored the preload="none" request and downloads the complete mp3 file.

Firefox network activity log shows a 200 OK response; Chromium, for example, shows 206 Partial Content.

Context

• Castopod: v.1.1.2 (using castopod-app and castopod-web-server from Docker Hub)
• OS: Debian 11
• Browser: Firefox 109.01 on Linux
• Web server: Nginx container, behind Caddy reverse-proxy
• Chromium version tested (not affected): 110.0.5481.77

Possible fixes

Upstream bug in Vime player?