fix(call): recover call audio when autoplay is blocked

[Antreesy]

☑️ Resolves

• Remote audio elements relied only on the "autoplay" attribute and never called play(), so when the browser blocked autoplay (e.g. a first-time guest with no media-engagement score) the participant heard no one and no error surfaced.
• Play elements explicitly and, on NotAllowedError, retry playback on the next user gesture. In mixAudio mode this also resumes the AudioContext, which starts suspended on Safari until a user gesture.

AI (if applicable)

• The content of this PR was partly or fully generated using AI

🖌️ UI Checklist

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required