GHSA-wvr4-3wq4-gpc5: MCP Connect has unauthenticated remote OS command execution via /bridge endpoint

When AUTH_TOKEN and ACCESS_TOKEN environment variables are not set (which is the default out-of-the-box configuration) the /bridge HTTP endpoint is completely unauthenticated. Any network-accessible caller can POST a request with an attacker-controlled serverPath and args payload, causing the server to spawn an arbitrary OS process as the user running mcp-bridge. This results in full remote code execution on the host without any credentials.