revert(ci): switch build stage back to node

.gitlab-ci.yml

@@ -8,13 +8,12 @@ stages:
 build_stage:
   stage: build
   # use node docker image as enviroment
-  image: oven/bun:canary-debian
+  image: node:latest
   script:
     # install & build the NuxtJS application
-    - apt update && apt-get install -y --no-install-recommends python3
-    - bun install
+    - yarn install
     - sed -Ei "s,(hasMigrated = )false,\1true," ${CI_PROJECT_DIR}/lib/dbconfig.ts
-    - NODE_ENV=production bun run --bun build
+    - NODE_ENV=production yarn run build
   # define artifacts which are shared between stages
   artifacts:
     paths: