feat(gateway): 优化OpenAI适配器实现

1. 使用bufio.Scanner代替io.ReadLine进行流式读取，提高效率
2. MapError返回ProviderError结构化错误码，便于错误处理和追踪
3. 更新go.mod添加必要依赖

gateway/go.mod

@@ -3,10 +3,19 @@ module lijiaoqiao/gateway
 go 1.21
 
 require (
-	github.com/golang-jwt/jwt/v5 v5.2.0
+	github.com/jackc/pgx/v5 v5.5.0
+	github.com/stretchr/testify v1.8.1
 )
 
 require (
-	github.com/jackc/pgx/v5 v5.5.0
-	golang.org/x/net v0.19.0
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
+	github.com/jackc/puddle/v2 v2.2.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/objx v0.5.0 // indirect
+	golang.org/x/crypto v0.9.0 // indirect
+	golang.org/x/sync v0.1.0 // indirect
+	golang.org/x/text v0.9.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )