fix: group rogue user counts by matrix instance in getMatrixStats function

repositories/matrix/MatrixRepository.js

@@ -223,6 +223,7 @@ async function getMatrixStats() {
       FROM user_tree_edges
       WHERE matrix_instance_id IN (?)
         AND rogue_user = TRUE
+      GROUP BY matrix_instance_id
     `, [instanceIds]);
     const rogueMap = new Map(rogueRows.map(r => [Number(r.mid), Number(r.rogueCnt)]));