willchen96 stops a shared workflow from taking down the backend

The team traced an ugly failure on the workflow listing screen: when the app tried to look up the name and email of whoever had shared a workflow, a failure in that lookup could escape the usual safety net and crash the backend entirely. The fix catches those failures, returns a controlled error to the caller, and treats sharer-name enrichment as nice-to-have rather than load-bearing - if the lookup fails, the list still loads without the name attached.

The same pass also replaced a brute-force scan of up to a thousand user accounts with targeted lookups for only the people actually referenced on screen. That's a real cost win on any reasonably sized tenant. As a bonus, missing API keys for the major LLM providers now produce a clear error up front instead of a cryptic failure mid-call.