Update Dockerfile to use Node.js 20

Dockerfile

@@ -1,5 +1,5 @@
 # Stage 1: Build Frontend
-FROM node:18-alpine AS frontend-builder
+FROM node:20-alpine AS frontend-builder
 WORKDIR /app/frontend
 
 # Install dependencies
@@ -23,9 +23,9 @@ RUN apt-get update && apt-get install -y \
     build-essential \
     && rm -rf /var/lib/apt/lists/*
 
-# Install Node.js 18 (required to run Next.js production server)
+# Install Node.js 20 (required to run Next.js production server)
 # Using nodesource setup script
-RUN curl -fsSL https://deb.nodesource.com/setup_18.x | bash - \
+RUN curl -fsSL https://deb.nodesource.com/setup_20.x | bash - \
     && apt-get install -y nodejs
 
 WORKDIR /app