Initial scaffold: React/Vite/TS PWA + Express/Prisma/Postgres backend

Materialschein & Kabelrechner für BergVOLT Elektrotechnik, portiert von der
vorherigen Single-File-HTML-Version. Microsoft-Entra-ID-Login (MSAL), Projekt-
Dashboard statt einer Datei pro Kunde, Retour-Buchen-Zusammenführung, 111
Kabeltypen aus den offiziellen Meinhart-Datenblättern. gitops/ nach
PROX/deploy-standard: git-backed Portainer-Stack, versionierte Docker-Images,
CI-Commit-back auf gitops/stack.yml.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,29 @@
+# ── Frontend bauen (React + Vite + TS + PWA) ──
+FROM node:20-alpine AS client-build
+WORKDIR /app/client
+COPY client/package*.json ./
+RUN npm ci
+COPY client/ ./
+RUN npm run build
+
+# ── Backend bauen (Express + TS + Prisma) ──
+FROM node:20-alpine AS server-build
+WORKDIR /app/server
+COPY server/package*.json ./
+RUN npm ci
+COPY server/ ./
+RUN npx prisma generate
+RUN npm run build
+
+# ── Laufzeit-Image ──
+FROM node:20-alpine
+WORKDIR /app
+ENV NODE_ENV=production
+COPY --from=server-build /app/server/node_modules ./node_modules
+COPY --from=server-build /app/server/dist ./dist
+COPY --from=server-build /app/server/prisma ./prisma
+COPY --from=server-build /app/server/package.json ./package.json
+COPY --from=client-build /app/client/dist ./public
+
+EXPOSE 80
+CMD ["sh", "-c", "npx prisma migrate deploy && node dist/index.js"]