fix: stabilize Docker builds by standardizing on ARM64 and explicit stage naming (klz-2026 pattern)

packages/infra/docker/Dockerfile.gatekeeper

@@ -1,10 +1,9 @@
-FROM node:20-alpine AS base
+# Step 1: Builder stage
+FROM node:20-alpine AS builder
 RUN apk add --no-cache libc6-compat curl
 WORKDIR /app
 RUN corepack enable pnpm
 
-# Step 2: Builder stage
-FROM base AS builder
 # Copy source (honoring .dockerignore)
 COPY . .
 
@@ -17,8 +16,9 @@ RUN --mount=type=cache,target=/root/.local/share/pnpm/store/v3 \
 # Build Gatekeeper
 RUN pnpm --filter @mintel/gatekeeper build
 
-# Step 3: Runner stage
-FROM base AS runner
+# Step 2: Runner stage
+FROM node:20-alpine AS runner
+RUN apk add --no-cache libc6-compat curl
 WORKDIR /app
 ENV NODE_ENV=production
 RUN addgroup --system --gid 1001 nodejs