test: rebuild backend/test runner and wait for mysql

docker-compose-frontend.yml

@@ -54,6 +54,9 @@ services:
       SECRET_KEY: ${SECRET_KEY:-change_me_in_production}
       LOG_LEVEL: ${LOG_LEVEL:-INFO}
       DATABASE_URL: mysql+pymysql://harborforge:harborforge_pass@mysql:${MYSQL_PORT:-3306}/harborforge
+    depends_on:
+      mysql:
+        condition: service_healthy
     networks:
       - test-network