fix: upgrade to yarn 4 (stable)

ignore generated .yarn and .yarnrc.yml for now, still evaluating if it's
better practice to include it in the repo

.dockerignore

@@ -1,4 +1,6 @@
 .git
+.yarn
+.yarnrc.yml
 build
 incoming
 docker

.gitignore

@@ -1,4 +1,6 @@
 # app specific
+.yarn
+.yarnrc.yml
 build
 incoming
 logs

frontend/Dockerfile

@@ -1,15 +1,18 @@
 FROM node:lts-bookworm-slim
 
+ENV YARN_VERSION stable
+
 RUN apt-get update \
     && apt-get install -y libjpeg-turbo-progs \
     git \
     nasm \
     vim \
+    && yarn set version $YARN_VERSION \
     && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 WORKDIR /code
 COPY package.json yarn.lock /code/
-RUN set -ex; yarn config set ignore-engines true; \
+RUN set -ex; \
     if [ "$NODE_ENV" = "production" ]; then \
         yarn install --no-cache --frozen-lockfile --production; \
     elif [ "$NODE_ENV" = "test" ] || [ "$NODE_ENV" = "e2e" ]; then \

frontend/package.json

@@ -65,5 +65,6 @@
     "vite": "^4.1.4",
     "vitest": "^0.29.1",
     "vue-tsc": "^1.2.0"
-  }
+  },
+  "packageManager": "yarn@4.0.2"
 }