[Feature] Add configuration for MCP tools and skills in the web and desktop clients

Summary

Add a feature to configure both MCP (Model Context Protocol) tools and skills directly in the web and desktop clients.

Currently, MCP tools and skills are configured through config files, which is not convenient for users of the web UI and desktop app. It would be helpful to provide a management interface where users can add, edit, and remove these configurations without editing files manually.

Proposed behavior

• A dedicated configuration page/section in both the web and desktop clients.
• Support add / edit / remove of MCP server entries (stdio / streamable HTTP / SSE transports).
• Support add / edit / remove of skills (skill definitions and their tool bindings).
• Validate the configuration and show connection/status information.
• Persist the configuration to the backend so it takes effect without a restart (or with a clear restart hint).

Additional context

This is a developer feedback item logged on behalf of the community.