refactor(docker): update Dockerfile for Next.js 15 and improve environment variable handling

dockerfile

@@ -1,48 +1,80 @@
-# Dockerfile for Next.js 14 - Optimized for Production
+# syntax=docker/dockerfile:1
+# Multi-stage Dockerfile for Next.js 15 (App Router, output: 'standalone')
+# Based on the official Next.js Docker example, tuned for Coolify.
+# Reference: https://github.com/vercel/next.js/blob/canary/examples/with-docker/Dockerfile
 
-# Use the official Node.js image with Alpine Linux for a smaller footprint
+# ----------------------------------------------------------------------------
+# Base image
+# ----------------------------------------------------------------------------
 FROM node:22-alpine AS base
-
-# Set the working directory in the container
+# libc6-compat is recommended by the Next.js image for some native deps (sharp, etc.)
+RUN apk add --no-cache libc6-compat
 WORKDIR /app
 
-# Copy package.json and package-lock.json (or yarn.lock)
-COPY package*.json ./
+# ----------------------------------------------------------------------------
+# 1. Dependencies — installed in a dedicated layer so they are cached as long
+#    as package.json / lockfile / .npmrc do not change.
+# ----------------------------------------------------------------------------
+FROM base AS deps
+COPY package.json package-lock.json .npmrc ./
+# Reproducible install honouring the lockfile (.npmrc provides legacy-peer-deps).
+RUN npm ci
 
-# Install dependencies - leveraging Docker cache
-RUN npm i --force 
+# ----------------------------------------------------------------------------
+# 2. Builder — produces the standalone output.
+#    NEXT_PUBLIC_* values are inlined into the client bundle at BUILD time,
+#    so they must be passed as build args. DEV_MODE is read in app/layout.js
+#    to enable Google Analytics, so it must also be present at build time.
+# ----------------------------------------------------------------------------
+FROM base AS builder
+WORKDIR /app
 
-# Copy the rest of the application code
+# Build-time arguments (Coolify: set these as Build Variables)
+ARG NEXT_PUBLIC_API_URL
+ARG NEXT_PUBLIC_CLIENT_ID
+ARG NEXT_PUBLIC_CLIENT_SECRET
+ARG DEV_MODE=FALSE
+
+# Expose them to `next build`
+ENV NEXT_PUBLIC_API_URL=$NEXT_PUBLIC_API_URL
+ENV NEXT_PUBLIC_CLIENT_ID=$NEXT_PUBLIC_CLIENT_ID
+ENV NEXT_PUBLIC_CLIENT_SECRET=$NEXT_PUBLIC_CLIENT_SECRET
+ENV DEV_MODE=$DEV_MODE
+ENV NEXT_TELEMETRY_DISABLED=1
+ENV NODE_ENV=production
+
+COPY --from=deps /app/node_modules ./node_modules
 COPY . .
 
-# Build the Next.js application
 RUN npm run build
 
-# Stage 2: Production image - smaller and leaner
-FROM node:22-alpine AS runner
-
-# Set the working directory
+# ----------------------------------------------------------------------------
+# 3. Runner — minimal production image running the standalone server.
+# ----------------------------------------------------------------------------
+FROM base AS runner
 WORKDIR /app
 
-# Set environment variables
-ENV NODE_ENV $NODE_ENV
-ENV NEXT_TELEMETRY_DISABLED 1 
+ENV NODE_ENV=production
+ENV NEXT_TELEMETRY_DISABLED=1
+# The standalone server must bind to all interfaces inside the container.
+ENV HOSTNAME=0.0.0.0
+ENV PORT=3000
 
-# Add a non-root user for security
-RUN addgroup -g 1001 -S nodejs
-RUN adduser -S nextjs -u 1001
+# Run as a non-root user for security.
+RUN addgroup --system --gid 1001 nodejs \
+  && adduser --system --uid 1001 nextjs
 
-# Copy only the necessary files from the builder stage
-COPY --from=base /app/next.config.js ./
-COPY --from=base /app/public ./public
-COPY --from=base --chown=nextjs:nodejs /app/.next/standalone ./
-COPY --from=base --chown=nextjs:nodejs /app/.next/static ./.next/static
+# Public assets (served by the standalone server).
+COPY --from=builder /app/public ./public
+
+# Standalone output already contains a minimal node_modules + server.js.
+COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
+# Static assets are NOT included in standalone and must be copied separately.
+COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
 
-# Change ownership of all copied files to the non-root user
 USER nextjs
 
-# Expose the port Next.js listens on
 EXPOSE 3000
 
-# Command to start the Next.js server in production mode
-CMD ["node", "server.js"]
+# server.js is generated by Next.js at the root of the standalone output.
+CMD ["node", "server.js"]