feat(docker): implement full frontend Next.js containerization and multi-service docker-compose

- Create multi-stage standalone Dockerfile for Next.js frontend (node:20-alpine, non-root nextjs:nodejs user)
- Configure output: 'standalone' in refer_landing_page/next.config.js
- Add refer_landing_page/.dockerignore for build context optimization
- Wire anl-backend and anl-frontend services in root docker-compose.yml with healthchecks, network dependencies, and persistent volume storage

refer_landing_page/Dockerfile

@@ -0,0 +1,54 @@
+# ==============================================================================
+# Stage 1: Install dependencies
+# ==============================================================================
+FROM node:20-alpine AS deps
+WORKDIR /app
+
+# Install libc6-compat for compatibility
+RUN apk add --no-cache libc6-compat
+
+COPY package.json package-lock.json ./
+RUN npm ci
+
+# ==============================================================================
+# Stage 2: Build the Next.js application
+# ==============================================================================
+FROM node:20-alpine AS builder
+WORKDIR /app
+
+COPY --from=deps /app/node_modules ./node_modules
+COPY . .
+
+# Set build-time environment variables
+ENV NEXT_TELEMETRY_DISABLED=1
+ENV NODE_ENV=production
+
+RUN npm run build
+
+# ==============================================================================
+# Stage 3: Production runner
+# ==============================================================================
+FROM node:20-alpine AS runner
+WORKDIR /app
+
+ENV NODE_ENV=production
+ENV NEXT_TELEMETRY_DISABLED=1
+ENV PORT=3000
+ENV HOSTNAME="0.0.0.0"
+
+RUN addgroup --system --gid 1001 nodejs && \
+    adduser --system --uid 1001 nextjs
+
+# Copy static assets and standalone build output
+COPY --from=builder /app/public ./public
+COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
+COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
+
+USER nextjs
+
+EXPOSE 3000
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+  CMD wget --no-verbose --tries=1 --spider http://localhost:3000 || exit 1
+
+CMD ["node", "server.js"]