feat(realtime): port set() method with timeout updates and cleanup

[AdirAmsalem]

Summary

Add the set() method to the realtime client.

Changes

• Add set() method: Implement set() method in realtime client with proper async/await handling
• Pydantic validation: Convert SetInput from dataclass to Pydantic BaseModel for robust input validation
• Cleanup: Remove unused SetAvatarImageMessage import from messages module
• Image handling: Improve URL parsing with proper data URI and HTTP(S) URL support
• Timeout configuration: Add timeout parameters to webrtc_manager for set() operations
• Tests: Add comprehensive unit tests covering set() method with various input scenarios

Testing

• Unit tests added for set() method with prompt, image, and enhance parameters
• Tested with data URIs, HTTP URLs, and binary image inputs
• Verified timeout handling and error cases
• All existing tests pass