Get Public Autorouter Presets

Return the auto-router preset catalog the dashboard's template picker renders.

Resolved once per process, like the model cost map: fetched from litellm.autorouter_presets_url (override with LITELLM_AUTOROUTER_PRESETS_URL) on the first request, falling back to the catalog bundled with the package on any failure. Set LITELLM_LOCAL_AUTOROUTER_PRESETS=True to serve the bundled catalog only. A restart picks up a newly published catalog.