Catalog: AI Management nav

## Jobs to be done (optional)

## Definition of done
Impact TBA

- Note: The impact of this is more than just Catalog. Removes the focus from Gateways as the primary entry point to AIGW (Gateways will just be one entry point, you can enter at the entity level. This does impact the UI, but also gives the impression that entities can exist outside of a Gateway now with optional? linkage to a Gateway).

### Open questions
- What is the scope of changes to the existing catalog now that it seems like this will be folded into AIGW? Will AIGW be the system of record for things that aren't proxied/governed (similar to how Catalog could record Agents/MCP servers that weren't in AIGW, but this could just be the Catalog underlayer and won't impact AIGW endpoints maybe)?
- Roles: Especially with MCP servers where they are creating one, what permissions do they need to see APIs/etc. that they can build an MCP server from?

## Information
See prototype: https://kongstrong.slack.com/archives/C068AHKGSPQ/p1788883136523559?thread_ts=1788876790.658079&cid=C068AHKGSPQ

## Due date (optional)

targeting summit for a demo, public release unlikely by summit

## Size