Fix ineffective restartInitiated guard with proper debouncing

The guard was setting and immediately resetting the flag in the same
synchronous execution, providing no actual protection. Now the flag
stays true until proxy reaches a stable state (running/exited/error)
via WebSocket notification, with additional client-side guard.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

resources/views/livewire/server/navbar.blade.php

@@ -181,6 +181,7 @@
                         }
                     });
                     $wire.$on('restartEvent', () => {
+                        if ($wire.restartInitiated) return;
                         window.dispatchEvent(new CustomEvent('startproxy'))
                         $wire.$call('restart');
                     });