Implement streaming endpoints with authentication

Add authenticated streaming endpoints that integrate with User Service JWT.

Prerequisites:

• User Service JWT authentication must be implemented first
• This issue is BLOCKED BY user-service issue #1

Endpoints:

• GET /api/streams (list active streams)
• POST /api/streams (create stream)
• GET /api/streams/{id} (get stream details)
• DELETE /api/streams/{id} (end stream)

Implementation:

• Validate JWT tokens from User Service
• Check user permissions
• Add streaming authorization logic
• Implement stream lifecycle management
• Add tests with mocked JWT validation