I haven't used the OpenGeoSuiteSDK lately but I guess you could just use the GetMap-URL which will probably look like this: http://localhost/cgi-bin/qgis_mapserv.fcgi?map=/home/hast/UA/qgis-mapnik.qgs
Have you tried the following yet?:
qgis: {
ptype: "gxp_wmssource",
url: "http://localhost/cgi-bin/qgis_mapserv.fcgi?map=/home/hast/UA/qgis-mapnik.qgs",
title: "Local QGIS MapServer",
version:"1.1.1"
},
{
source: "qgis",
title: "QGIS Server Layer",
layers: "buildings",
opacity: 1,
group: "overlays"
}