Add Dockerfile for Vite frontend (GHJ deploy pattern)

frontend/Dockerfile

@@ -1,26 +1,13 @@
-# syntax=docker/dockerfile:1
-
-# ===== STAGE 1: Build =====
-FROM node:22-alpine AS builder
-
-RUN corepack enable && corepack prepare pnpm@latest --activate
+FROM node:20-alpine AS build
 WORKDIR /app
-
-COPY package.json pnpm-lock.yaml ./
-RUN --mount=type=cache,id=pnpm-marketplace,target=/pnpm/store \
-    pnpm install --frozen-lockfile
-
+COPY package*.json ./
+RUN npm install
 COPY . .
-RUN pnpm build
+RUN npm run build
 
-# ===== STAGE 2: Production (static-web-server ~3MB binary) =====
-FROM docker.io/joseluisq/static-web-server:2-alpine
-
-COPY --from=builder /app/dist /public
-
-# SPA mode: fallback para index.html
-ENV SERVER_FALLBACK_PAGE=/public/index.html
-ENV SERVER_ROOT=/public
-ENV SERVER_PORT=3000
-
-EXPOSE 3000
+FROM node:20-alpine
+WORKDIR /app
+RUN npm install -g serve
+COPY --from=build /app/dist ./dist
+EXPOSE 8080
+CMD ["serve", "-s", "dist", "-l", "8080"]