style: 统一 input 包装类型为 []any，与正常 OAuth 路径一致

backend/internal/service/openai_gateway_request_body.go

@@ -581,7 +581,7 @@ func normalizeOpenAIPassthroughOAuthBody(body []byte, compact bool) ([]byte, boo
 			text := inputResult.String()
 			var inputValue any
 			if strings.TrimSpace(text) != "" {
-				inputValue = []map[string]any{{
+				inputValue = []any{map[string]any{
 					"type": "message", "role": "user", "content": text,
 				}}
 			} else {