docs: Remove obsolete volume_mode references from documentation

The volume_mode parameter is no longer used since workflows now upload files to MinIO storage instead of mounting volumes directly. This commit removes all references to volume_mode from:

- Backend API documentation (README.md)
- Tutorial getting started guide
- MCP integration guide
- CLI AI reference documentation
- SDK documentation and examples
- Test project documentation

All curl examples and code samples have been updated to reflect the current MinIO-based file upload approach.

docs/docs/tutorial/getting-started.md

@@ -186,8 +186,7 @@ For local files, you can use the upload endpoint:
 # Create tarball and upload
 tar -czf project.tar.gz /path/to/your/project
 curl -X POST "http://localhost:8000/workflows/security_assessment/upload-and-submit" \
-     -F "file=@project.tar.gz" \
-     -F "volume_mode=ro"
+     -F "file=@project.tar.gz"
 
 # Check status
 curl "http://localhost:8000/runs/{run-id}/status"