feat(console search): add concurrency cap or pagination for cross-catalog search data fetching

[vignesh-manel]

##Context

The search feature #187 fetches all catalogs, namespaces, tables, and views client-side when the search dialog opens. The fetch strategy fans out to one request per namespace for tables and views:

 1 request per catalog   → namespaces
 1 request per namespace → tables   ← fan-out
 1 request per namespace → views    ← fan-out

In a deployment with many catalogs this results in several parallel HTTP requests on first open.

Problem

• First open can be noticeably slow in large deployments
• Causes a request spike on the Polaris server

Proposed solution

• Implement a concurrency cap or pagination

[jbonofre]

Thanks @vignesh-manel ! It's what we discussed in the #187 PR. Much appreciated !