Registering Tokens (tokens/register)

[leogdion]

[leogdion]

Status Update: The registerToken operation exists in Sources/MistKit/Generated/Client.swift (line 3174) but is not exposed in the public CloudKitService API.

What needs to be done:

1. Create a public wrapper method in CloudKitService+Operations.swift
2. Support APNs token registration with CloudKit
3. Add documentation explaining token registration flow
4. Handle token refresh and device token updates
5. Add tests for token registration scenarios

Generated operation signature:

internal func registerToken(_ input: Operations.registerToken.Input) 
  async throws -> Operations.registerToken.Output

Part of push notification support (#52, #53) - completes the APNs integration story.