Fix Dockerfile with multi-stage build for frontend

Dockerfile

@@ -1,24 +1,22 @@
-FROM python:3.10-slim
-
-WORKDIR /app
+# Multi-stage build: Build frontend with Node.js
+FROM node:18-alpine AS frontend-builder
 
-# Install Node.js for building frontend
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    build-essential \
-    curl \
-    && curl -fsSL https://deb.nodesource.com/setup_18.x | bash - \
-    && apt-get install -y nodejs \
-    && rm -rf /var/lib/apt/lists/*
-
-# Build frontend
-COPY frontend/package*.json ./frontend/
 WORKDIR /app/frontend
+
+COPY frontend/package*.json ./
 RUN npm install
-COPY frontend/ .
+
+COPY frontend/ ./
 RUN npm run build
 
+# Main stage: Python app
+FROM python:3.10-slim
+
 WORKDIR /app
 
+# Copy built frontend
+COPY --from=frontend-builder /app/frontend/dist ./frontend/dist
+
 # Install Python dependencies
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt