feat: WebSocket connection pool for Flask-to-OpenClaw redundancy

[MCERQUA]

Problem

Single persistent WebSocket from Flask to OpenClaw. If it disconnects mid-request, reconnection + retry adds latency.

Current Behavior

• One WebSocket connection with exponential backoff reconnection
• Disconnect during request → backoff delay → retry → user waits

Solution

Maintain a pool of 2 WebSocket connections. If one disconnects mid-request, failover to the other immediately.

Priority: LOW (current single connection is stable)

Files

• services/gateways/openclaw.py