fix: remove nginx, serve frontend from Express on port 3000, fix static path

Dockerfile

@@ -18,11 +18,11 @@ COPY backend/ ./
 RUN npx prisma generate --schema=src/prisma/schema.prisma
 RUN npm run build
 
-# Stage 3: Production (Debian slim to match build stage, avoiding Alpine musl/OpenSSL issues)
+# Stage 3: Production (Debian slim — same glibc as build, no musl/OpenSSL issues)
 FROM node:20-slim
 WORKDIR /app
 
-RUN apt-get update && apt-get install -y nginx openssl --no-install-recommends && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y openssl --no-install-recommends && rm -rf /var/lib/apt/lists/*
 
 # Copy backend
 COPY --from=backend-build /app/backend/dist ./dist
@@ -30,15 +30,12 @@ COPY --from=backend-build /app/backend/node_modules ./node_modules
 COPY --from=backend-build /app/backend/src/prisma ./prisma
 COPY backend/package.json ./package.json
 
-# Copy frontend build
+# Copy frontend build — served by Express at /app/public
 COPY --from=frontend-build /app/frontend/dist ./public
 
-# Nginx config
-COPY nginx.conf /etc/nginx/nginx.conf
-
 COPY start.sh ./
 RUN chmod +x start.sh
 
-EXPOSE 80
+EXPOSE 3000
 
 CMD ["./start.sh"]