Add real-time market data streaming via WebSocket

[Smartdevs17]

Description

Provide real-time market data (interest rates, pool utilization, liquidations) via WebSocket for external integrators and frontend dashboards.

Acceptance Criteria

• WebSocket server with connection management
• Channel-based subscriptions (pools, liquidations, rates)
• Throttled updates (max 1 per second per channel)
• Reconnection with state recovery
• Authentication for private channels
• Fallback to polling on WebSocket failure

Technical Scope

• api/src/ws/
• oracle/src/services/
• Edge: connection spike on market events, message ordering, rate limit per connection