Fix docker file for prod

Dockerfile.prod

@@ -45,3 +45,12 @@ USER nextjs
 EXPOSE 3000
 
 CMD ["bun", "./server.js"]
+
+# One-off migrations image (run at deploy time with DATABASE_URL)
+FROM base AS migrate
+WORKDIR /app
+COPY --from=deps /app/node_modules ./node_modules
+COPY prisma ./prisma
+COPY prisma.config.ts package.json ./
+ENV NODE_ENV=production
+CMD ["bunx", "prisma", "migrate", "deploy"]