feat: add Dockerfile for frontend service

Introduce a multi-stage Dockerfile for the frontend service to enable efficient builds and an optimized runtime using Node.js 22.

frontend/Dockerfile

@@ -0,0 +1,22 @@
+FROM node:22-slim AS base
+ENV PNPM_HOME="/pnpm"
+ENV PATH="$PNPM_HOME:$PATH"
+RUN corepack enable
+
+FROM base AS build
+WORKDIR /usr/src/app
+COPY . .
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store pnpm install --frozen-lockfile
+RUN pnpm run --filter @memegoat/frontend build
+
+FROM base AS runtime
+WORKDIR /app
+COPY --from=build /usr/src/app/frontend/public ./frontend/public
+COPY --from=build /usr/src/app/frontend/.next/standalone ./
+COPY --from=build /usr/src/app/frontend/.next/static ./frontend/.next/static
+
+EXPOSE 3000
+ENV PORT=3000
+ENV HOSTNAME="0.0.0.0"
+
+CMD ["node", "frontend/server.js"]