[Feature] WebSocket Real-time Chain/Swarm Updates

[yedidyakfir]

Description

Add real-time status updates to mageflow visualizer.

Blocked by: #47

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Events to Emit

• task.started, task.completed, task.failed
• chain.completed, chain.failed
• swarm.progress, swarm.completed, swarm.failed

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Tasks

• Add WebSocket endpoint to visualizer
• Emit events from external service
• Update visualizer frontend to consume events
• Test with concurrent chains/swarms

Key Files

• /mageflow/visualizer/server.py