fix(webcam): fix some connection issues in Camera-Streamer

[meteyou]

Description

This PR fix these WebRTC connection issues:

• double connections
• terminate session when backend is not available
• start/stop when open/close panel on the dashboard
• start stream in webcam page, when dashboard panel is closed

Related Tickets & Documents

none

Mobile & Desktop Screenshots/Recordings

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[optional] Are there any post-deployment tasks we need to perform?

none