fix: switch Dockerfile base image to alpine and install dependencies using apk

Dockerfile

@@ -1,9 +1,9 @@
-FROM node:20-slim
+FROM alpine
 
-# force rebuild to ensure git is installed
+RUN apk add --no-cache nodejs npm git \
-RUN apt-get update && apt-get install -y --no-install-recommends \
+    && node --version \
-    git \
+    && npm --version \
-    && rm -rf /var/lib/apt/lists/*
+    && git --version
 
 WORKDIR /action
 

app/git.js

@@ -11,7 +11,9 @@ function git(args, cwd) {
 
 export async function commitAndPush(workspace) {
   const repoDir = path.join(workspace, GITEA_REPOSITORY);
-  const remoteUrl = GITEA_SERVER_URL.replace(/\/$/, '').replace('https://', `https://${GITEA_TOKEN}@`).replace('http://', `http://${GITEA_TOKEN}@`) + `/${GITEA_REPOSITORY}.git`;
+  const remoteUrl = GITEA_SERVER_URL.replace(/\/$/, '')
+    .replace('https://', `https://${GITEA_TOKEN}@`)
+    .replace('http://', `http://${GITEA_TOKEN}@`) + `/${GITEA_REPOSITORY}.git`;
 
   try {
     git(['config', 'user.email', 'ai-review[bot]@gitea'], repoDir);