Rebrand project: DocumentOperator to DocumentService

This commit implements a complete rebranding of the project:
- Updated all namespaces from `DocumentOperator` to `DocumentService`.
- Renamed file paths, embedded resources, and test data references.
- Updated configuration keys, logging paths, and Redis instance names.
- Revised documentation to reflect the new project name.
- Modified project and solution files to align with the new structure.
- Updated class names, DTOs, commands, queries, and handlers.
- Adjusted middleware, controllers, and API endpoints.
- Updated Swagger metadata and API titles to `DocumentService API`.
- Refactored test namespaces, resource paths, and embedded resources.
- Updated build and deployment configurations for the new name.
- Replaced all references to `DocumentOperator` in comments and literals.

These changes ensure consistency across the codebase and documentation.

REQUIRED_FEATURES.md

@@ -1,4 +1,4 @@
-# DocumentOperator - Required Functions and Features
+# DocumentService - Required Functions and Features
 
 **Project:** DocumentService (DOC)  
 **Ticket:** DOC-1 - GDPicture and Nutrient Replacing  
@@ -9,7 +9,7 @@
 
 ## Overview
 
-This document describes in detail all PDF processing functions that the DocumentOperator service must implement. These functions will be implemented using the DevExpress Office File API as a replacement for the GDPicture and Nutrient libraries.
+This document describes in detail all PDF processing functions that the DocumentService service must implement. These functions will be implemented using the DevExpress Office File API as a replacement for the GDPicture and Nutrient libraries.
 
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@@ -548,7 +548,7 @@ Body: {
 - **DevExpress PDF API Documentation:** https://docs.devexpress.com/OfficeFileAPI/
 - **PDF/A Standard:** ISO 19005
 - **ZUGFeRD Standard:** https://www.ferd-net.de/
-- **Ticket:** DOC-1 (M:\Austausch\DocumentOperator)
+- **Ticket:** DOC-1 (M:\Austausch\DocumentService)
 
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