Refactored the `Handle` method in `ReadDocumentQueryHandler` to
eagerly load related data (`Elements` and `Annotations`) using
`Include` and `ThenInclude`. Introduced a reusable `docQuery`
variable to reduce code duplication and ensure consistency in
queries for both `query.Id` and `query.EnvelopeId`. No changes
were made to the mapping logic or exception handling.
- Updated DocumentController to use class-level [Authorize] and method-level role-based authorization for sender and receiver endpoints.
- Replaced ReadEnvelopeReceiverQuery with ReadDocumentQuery for sender document retrieval; simplified response logic.
- Added a new endpoint for fully authenticated receivers to fetch documents by envelope ID from user claims.
- Refactored ReadDocumentQuery and handler to always return DocumentDto, throw NotFoundException when needed, and use _repo.Query.
- Cleaned up using directives and removed legacy error handling and logging.
