AI root-cause diagnosis for one provider's DVM Production drill-down (PAW-576). POST since it may trigger an LLM call; the result is cached server-side.

AI root-cause diagnosis for one provider's drill-down on the DVM Production tab (PAW-576). bool DvmDiagnosisDto.IsLlmGenerated is false when the deterministic rule-based fallback was used (LLM call failed or returned nothing).