BUG: Potential goroutine leak in IDLE watcher cleanup

[andrinoff]

Describe the bug
In fetcher/idle.go, Watch() creates goroutines but comment "Let old connection tear down in the background" suggests goroutines may not be properly waited on, risking leaks if connections don't close cleanly.

To reproduce
Examine fetcher/idle.go lines 48-60:

// Stop existing watcher for this account if any
if existing, ok := w.watchers[account.ID]; ok {
    close(existing.stop)
    delete(w.watchers, account.ID)
    // Let old connection tear down in the background
}

If old connection hangs, goroutine never exits.

Expected behavior
Use WaitGroup or ensure goroutines terminate within timeout.

Additional context

• Good first issue
• StopAllAndWait() exists but only called on shutdown
• Long-running background goroutines can accumulate

Suggested fix:
Add timeout-based cleanup or WaitGroup tracking.

OS
All platforms