Introduce a 4-step modal wizard on SenderPage for creating envelopes.
Validate required fields, support optional skip, receiver management, PDF upload, and keyboard shortcuts.
Persist wizard payload in sessionStorage via token-based bootstrap service and navigate to editor with bootstrapToken.
Register bootstrap storage service in both client and server DI containers and add dedicated sender wizard styling.
Changed the `ILogger` dependency injection type parameter from `EnvelopeSenderPage` to `SenderPage` to ensure alignment with the correct class name or intended logging context.
