chore(deps): pin dependencies

Change-Id: I44bb272cd38668f4ecd44ba9fe97c97cdb0b08a7
diff --git a/docker-compose.yml b/docker-compose.yml
index ca974ad..0b3b1b9 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -26,7 +26,7 @@
       - backend
     restart: unless-stopped
   db:
-    image: mariadb
+    image: mariadb@sha256:9da6213d1a5714c4585c9c0003c51510b320d6f60e53d78701fe1e194126249f
     environment:
       MYSQL_ALLOW_EMPTY_PASSWORD: "yes"
       MARIADB_DATABASE: twpt