[upstream #16245] #16245: Match endpoint names with surrounding whitespace in the list filter

[berry-13]

From LibreChat-AI#16245 (LibreChat-AI#16245 (comment)).

parseEndpoints trims each requested endpoint name, but endpointSchema permits custom endpoint names with leading or trailing whitespace and conversations store the name verbatim, so filtering by such an endpoint matches nothing. Either match the exact configured value (trim only to detect blank entries) or normalize endpoint names at the config and persistence boundaries.