Sync LiteLLM models and groups

Reads the LiteLLM proxy with the stored organization key (org mode) or admin key (member mode) and refreshes the provider's models. Org mode refreshes the "All LiteLLM models" group. Member mode refreshes team groups, re-checks every connected member key, moves members to the group matching their key's models, revokes keys LiteLLM rejects, and removes automatic grants of people who may no longer connect. A failed read keeps the last synced catalog and records the error. Requires the Manage Gateway providers permission and Gateway management.