Add SMTP mail utility, admin settings page, and API routes for SMTP configuration and test email

Dockerfile

@@ -9,6 +9,8 @@ WORKDIR /app
 # Install dependencies (use package lock when present)
 COPY shop/package*.json ./
 RUN npm ci --omit=dev
+# Install nodemailer for email sending
+RUN npm install nodemailer
 
 # Copy the source code
 COPY shop/ .
@@ -23,14 +25,16 @@ WORKDIR /app
 
 # Copy only built assets and runtime dependencies
 COPY --from=builder /app/.next ./.next
-
+# Copy standalone server and static assets
+COPY --from=builder /app/.next/standalone ./
+COPY --from=builder /app/.next/static ./.next/static
 # KORREKTUR: Kopiert den public-Ordner nur, wenn er wirklich existiert
 COPY --from=builder /app/public* ./public
 
 COPY --from=builder /app/package*.json ./
 # KORREKTUR: Flexibles Kopieren der Next-Konfiguration (egal ob .js oder .mjs)
 COPY --from=builder /app/next.config.* ./
-# Optionale TS-Dateien (nur kopieren, wenn vorhanden, blockiert den Build nicht mehr)
+# KORREKTUR: Optionale TS-Dateien über den Sternchen-Trick absichern
 COPY --from=builder /app/tsconfig.jso* ./
 COPY --from=builder /app/next-env.d.t* ./
 # Install production dependencies (already installed in builder, but ensure they are present)
@@ -42,5 +46,5 @@ ENV PORT=3000
 
 EXPOSE 3000
 
-# Start the Next.js server
-CMD ["npm", "run", "start"]
+# Start the Next.js server (standalone)
+CMD ["node", "server.js"]