Drop qt_users dependency for configs and track app version

migrations/007_detach_configurations_from_qt_users.sql

@@ -0,0 +1,25 @@
+-- Detach qt_configurations from qt_users (ownership is owner_username text)
+-- Safe for MySQL 8+/MariaDB 10.2+ via INFORMATION_SCHEMA checks.
+
+SET @fk_exists := (
+    SELECT COUNT(*)
+    FROM information_schema.TABLE_CONSTRAINTS
+    WHERE CONSTRAINT_SCHEMA = DATABASE()
+      AND TABLE_NAME = 'qt_configurations'
+      AND CONSTRAINT_NAME = 'fk_qt_configurations_user'
+      AND CONSTRAINT_TYPE = 'FOREIGN KEY'
+);
+
+SET @drop_fk_sql := IF(
+    @fk_exists > 0,
+    'ALTER TABLE qt_configurations DROP FOREIGN KEY fk_qt_configurations_user',
+    'SELECT ''fk_qt_configurations_user not found, skip'' '
+);
+PREPARE stmt_drop_fk FROM @drop_fk_sql;
+EXECUTE stmt_drop_fk;
+DEALLOCATE PREPARE stmt_drop_fk;
+
+-- user_id becomes optional legacy column (can stay NULL)
+ALTER TABLE qt_configurations
+    MODIFY COLUMN user_id BIGINT UNSIGNED NULL;
+