8a375749f1
- Add DefaultLanguage() that reads WEKNORA_LANGUAGE env with zh-CN fallback - Replace hardcoded zh-CN in LanguageNameFromContext with DefaultLanguage() - Unify middleware/language.go to use types.DefaultLanguage() - Add Language field to DocumentProcessPayload (8 enqueue sites + worker restore) - Add Language field to ImageMultimodalPayload (enqueue + worker restore) - Propagate language from ImageMultimodalPayload to QuestionGenerationPayload