feat(tools): add Solution Explorer file and reference management tools

[CalvinAllen]

Description

Add tools to manage project files and references from the Solution Explorer.

Tools to Implement

Tool	Description
project_add_file	Add an existing file to a project
project_remove_file	Remove a file from a project
project_add_reference	Add a project-to-project reference
project_remove_reference	Remove a reference from a project

Notes

• Competitor reference: Unofficial VS MCP Server by dhq-boiler