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.

DocumentOperator.API/README.md

@@ -1,6 +1,6 @@
-# DocumentOperator API - Manual Testing Guide
+# DocumentService API - Manual Testing Guide
 
-This guide contains manual test scenarios for validating the DocumentOperator API endpoints using Swagger UI or tools like Postman.
+This guide contains manual test scenarios for validating the DocumentService API endpoints using Swagger UI or tools like Postman.
 
 ---
 
@@ -8,7 +8,7 @@ This guide contains manual test scenarios for validating the DocumentOperator AP
 
 1. **Start the API:**
    ```powershell
-   dotnet run --project DocumentOperator.API
+   dotnet run --project DocumentService.API
    ```
    Default URL: `https://localhost:5001` (check console output for actual port)