[FEATURE]: Make MCP app setup discoverable in Settings #18995

Problem

A user wanted to add a new MCP and could not find the button to do it. They expected an Add Apps entry point in Settings, but it appears to be missing or too hidden.

Feedback

• Add Apps is not discoverable from the main Settings flow
• MCP setup is currently hidden under Advanced, which is easy to miss
• As more configuration moves into Settings, MCP onboarding should be visible there too

Requested change

Surface a clear Add Apps / Add MCP entry point directly in Settings instead of burying it under Advanced.

Why

Adding an MCP is a core setup action, so the UI should make that path obvious without users needing to guess that it lives in an advanced section.