Make MCP endpoints configurable

**What problem will this feature request solve?**
It would be great to open the scope of MCP capabilities/api endpoints. But some Metabase admins may not want users programmatically generating lots of content (e.g. maybe they only want the MCP to read in existing charts). It would be nice for the MCP to be configurable via a set of toggles (e.g. create content in personal collections, create content in shared collections, edit existing content in personal collections, edit existing content in shared collections).

**Describe the solution you'd like.**
This request is a little strange because the MCP already respects individual permissions via Oauth. I'm assuming some people want different permissions for themselves + robot vs. themselves alone. An alternative approach is having a clear review system to decide whether you want to merge your MCP-generated content to non-personal collections (though that's not mutually exclusive with the configurable endpoint approach).

**How does this feature request impact you?**
The ability to scope MCP for an instance means we could add more endpoints.

The issue names no files, tests, or entry points. Start by locating the MCP endpoint implementation and its existing OAuth and permission checks, then map the endpoint categories and administration configuration surfaces. Done should include a defined scope for create and edit operations in personal and shared collections, with coverage for allowed and disallowed cases.

Written by the indexing model from the issue text.