Feat: Add broadcasting subsystem (drivers + channel auth)

[3m1n3nc3]

Background: Real-time features need an abstracted broadcast layer supporting multiple drivers (Pusher, Redis, WebSocket, log), plus channel authorization.

Tasks:

• Create a @h3ravel/broadcast package in the framework/packages directory.
• Define BroadcastManager and driver contract.
• Implement at least two drivers (e.g., log and redis or a simple in-process WS).
• Implement channel auth middleware for private/guarded channels.
• Provide event interface (shouldBroadcast, broadcastOn channels).
• Add integration tests for broadcasting events and auth checks.
• Document configuration and examples.

Acceptance criteria:

• App can broadcast events via chosen driver.
• Private channel authorization flow works (authenticated user allowed/denied).
• Interface mirrors laravel as much as possible, creating the familiar DX while also adding it own unique twists and turns.
• Tests cover driver behavior.

Difficulty: large