fix(prisma): make owner FK migration resilient on MariaDB

backend/prisma/migrations/20260502160000_product_owner_required/migration.sql

@@ -14,9 +14,27 @@ DELETE FROM `Product` WHERE `ownerId` IS NULL;
 ALTER TABLE `Product`
   MODIFY COLUMN `ownerId` INT NOT NULL;
 
--- Steg 4: Uppdatera foreign key constraint till CASCADE (ta bort gammal, lägg till ny)
-ALTER TABLE `Product`
-  DROP FOREIGN KEY IF EXISTS `Product_ownerId_fkey`;
+-- Steg 4: Uppdatera foreign key constraint till CASCADE
+-- Droppa befintlig FK på ownerId med dynamiskt namn (miljöer kan skilja sig).
+SET @fk_name := (
+  SELECT kcu.CONSTRAINT_NAME
+  FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu
+  WHERE kcu.TABLE_SCHEMA = DATABASE()
+    AND kcu.TABLE_NAME = 'Product'
+    AND kcu.COLUMN_NAME = 'ownerId'
+    AND kcu.REFERENCED_TABLE_NAME = 'User'
+  LIMIT 1
+);
+
+SET @drop_fk_sql := IF(
+  @fk_name IS NULL,
+  'SELECT 1',
+  CONCAT('ALTER TABLE `Product` DROP FOREIGN KEY `', @fk_name, '`')
+);
+
+PREPARE stmt_drop_fk FROM @drop_fk_sql;
+EXECUTE stmt_drop_fk;
+DEALLOCATE PREPARE stmt_drop_fk;
 
 ALTER TABLE `Product`
   ADD CONSTRAINT `Product_ownerId_fkey`