Multiple Sessions Support

Opening the site in multiple browser tabs causes websockets to cascade and reconnect repeatedly - each new connection closes the previous one, which then tries to reconnect, creating an endless loop of disconnections. The frontend wasn't designed with multi-tab usage in mind, but users naturally open multiple tabs.

Additionally, when build completion notifications fire, every open tab will try to play the notification sound simultaneously, which is annoying and redundant.

Goals:

• Support multiple tabs without connection cascades
• Ensure most state updates are idempotent (might already be the case)
• Only play notification sound in one tab, preferably the most recently active one
• Handle autoplay restrictions gracefully (if one tab can't play audio, try another)