WebSocket endpoint for real-time bidirectional communication.

This endpoint establishes a WebSocket connection and:

• Streams events to the client whenever flows are created, updated, deleted, started, or stopped
• Sends ping messages every 15 seconds to keep the connection alive
• Handles pong responses from the client

Example usage from JavaScript:

const ws = new WebSocket('ws://localhost:3000/api/ws');
ws.onmessage = (event) => {
    const data = JSON.parse(event.data);
    console.log('Received event:', data);
};
ws.onclose = () => console.log('Disconnected');
ws.onerror = (error) => console.error('WebSocket error:', error);