Improvement: proxy-sovd - Handle SOVD errors[] array in DataResponse - map field-level errors to UDS NRCs

[arvindr19]

Description

Map SOVD errors[] array to UDS NRCs

DataResponse deserialises the errors[] array from SOVD but field-level errors are not currently mapped to UDS Negative Response Codes. This causes silent failures for partial-error responses.

• Inspect DataResponse.errors after each SOVD call
• Map known SOVD error codes/types to appropriate Nrc values (e.g. ConditionsNotCorrect, RequestOutOfRange)
• Add unit tests covering error → NRC mapping

Additional Context

File: proxy-sovd/src/schema.rs, proxy-sovd/src/mapper.rs
PR: #12