Expand health endpoint with system metrics

[dennisthemenacing]

Feature Request\n\nThe endpoint in currently returns only . This is minimal for production monitoring.\n\nCurrent response:\n\n\nProposed additions:\n- — stats (heapUsed, heapTotal, external, rss)\n- — count of current Socket.io connections\n- — number of active games in GameManager\n\nThis helps operators monitor resource usage and load without additional infrastructure.\n\nFiles likely affected:\n- — add metrics to the health response\n- The endpoint already exists, so no new routes needed\n\nThis is a good first issue for someone wanting to contribute — minimal scope, self-contained, no need to understand the full codebase.