[O2B-1539] Add index on QC flags to help GAQ summary computation (#2099)

* Add a composite index on quality_control_flags(run_number, detector_id) that proved to reduce computation time for GAQ summary by approx 50% with the caveat it was tested only on a local machine.

Author: isaachilly

lib/database/migrations/v1/20260305110000-add-qcf-run-detector-index.js

@@ -0,0 +1,28 @@
+/*
+ *  @license
+ *  Copyright CERN and copyright holders of ALICE O2. This software is
+ *  distributed under the terms of the GNU General Public License v3 (GPL
+ *  Version 3), copied verbatim in the file "COPYING".
+ *
+ *  See http://alice-o2.web.cern.ch/license for full licensing information.
+ *
+ *  In applying this license CERN does not waive the privileges and immunities
+ *  granted to it by virtue of its status as an Intergovernmental Organization
+ *  or submit itself to any jurisdiction.
+ */
+
+'use strict';
+
+/** @type {import('sequelize-cli').Migration} */
+module.exports = {
+    up: async (queryInterface) => queryInterface.sequelize.transaction(async (transaction) => {
+        await queryInterface.addIndex('quality_control_flags', {
+            name: 'quality_control_flags_run_detector_idx',
+            fields: ['run_number', 'detector_id'],
+        }, { transaction });
+    }),
+
+    down: async (queryInterface) => queryInterface.sequelize.transaction(async (transaction) => {
+        await queryInterface.removeIndex('quality_control_flags', 'quality_control_flags_run_detector_idx', { transaction });
+    }),
+};