feat: add zoom_in and zoom_out commands to PTZ command map

note: the `API.md` said it's `zoom_in` and `zoom_out` with underscore, while the go ptzCmdMap said it's `zoomin` and `zoomout` with underscore; I choose to support both (or unify them?)

pkg/service/ptz_test.go

@@ -159,7 +159,7 @@ func TestPTZCmdMap(t *testing.T) {
 	// 验证所有预定义的命令都存在
 	expectedCommands := []string{
 		"stop", "right", "left", "down", "downright", "downleft",
-		"up", "upright", "upleft", "zoomin", "zoomout",
+		"up", "upright", "upleft", "zoomin", "zoomout", "zoom_in", "zoom_out",
 	}
 
 	for _, cmd := range expectedCommands {