Introduced `ReadDocReceiverElementQuery` for retrieving document receiver elements and its corresponding handler. Added necessary `using` directives for dependencies like `AutoMapper`, `MediatR`, and `Microsoft.EntityFrameworkCore`.
The handler dynamically filters `DocReceiverElement` data based on optional query parameters (e.g., `Envelope.Id`, `Envelope.Uuid`, `Receiver.Id`, `Receiver.Signature`) using LINQ. Data is fetched asynchronously and mapped to DTOs using `AutoMapper`.
Introduced the `SaveSignatureBehavior` class as a pipeline behavior for handling `SigningCommand` requests. Added necessary `using` directives to include required namespaces. Resolved merge conflicts in `using` directives between `net8.0` and `net9.0` project versions. Implemented the `Handle` method to delegate request processing.
Added a new `SignatureDto` record to represent captured signatures with metadata, including properties like `ElementId`, `DataUrl`, `FullName`, `Position`, and `Place`. Updated `SigningCommand` to include a `Signatures` property for handling multiple signatures, deprecating `PsPdfKitAnnotation`.
Introduced a `MappingProfile` class to map `SignatureDto` to `DocReceiverElement` using AutoMapper. Added necessary `using` directives to support the new mapping configuration.
