Store configuration owner by MariaDB username

migrations/005_add_owner_username.sql

@@ -0,0 +1,10 @@
+-- Store configuration owner as username (instead of relying on numeric user_id)
+ALTER TABLE qt_configurations
+    ADD COLUMN owner_username VARCHAR(100) NOT NULL DEFAULT '' AFTER user_id,
+    ADD INDEX idx_qt_configurations_owner_username (owner_username);
+
+-- Backfill owner_username from qt_users for existing rows
+UPDATE qt_configurations c
+LEFT JOIN qt_users u ON u.id = c.user_id
+SET c.owner_username = COALESCE(u.username, c.owner_username)
+WHERE c.owner_username = '';