Fix Docker npm ci by switching build image to Node 20.

Avoid the node:22-alpine crash that fails installs with Exit handler never called.

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -1,10 +1,10 @@
-FROM docker.arvancloud.ir/node:22-alpine AS build
+# node:22-alpine npm often dies with "Exit handler never called" in Docker builds.
+FROM docker.arvancloud.ir/node:20-alpine AS build
 
 WORKDIR /app
 
 COPY package.json package-lock.json ./
-RUN --mount=type=cache,target=/root/.npm \
-    npm ci --no-audit --no-fund
+RUN npm ci --no-audit --no-fund
 
 COPY . .