Migrate docs and container setup to full Next.js workflow

[kabeier]

Motivation

• Align project documentation and container configuration with the app's current Next.js setup instead of legacy Webpack guidance.
• Ensure development and production container flows run a Next.js server (next dev / next start) rather than statically serving a Webpack build.
• Consolidate ports and Makefile targets for a predictable developer experience.

Description

• Rewrote README.md to describe a Next.js-based stack, update local/dev/prod commands, and remove Webpack-specific wording and preview steps.
• Replaced the runtime stage in Dockerfile to a Node-based Next.js runtime that runs npm run start and copies the .next build output and pages into the image.
• Updated docker-compose.yml and docker-compose.override.yml to use port 4173 consistently and run the Next.js dev server on that port with the appropriate dev command arguments.
• Updated Makefile to replace the obsolete preview target with a start target and keep other convenience targets in sync with Next.js commands.

Testing

• Ran npm run typecheck which completed successfully (tsc --noEmit).
• Ran rg -n "webpack" --glob '!package-lock.json' which showed no remaining references to Webpack outside of package-lock.json.
• Attempted docker compose config but the Docker CLI is not available in this environment so container config could not be validated.
• Attempted npm run build in this environment but the Next.js runtime binary could not be resolved here, so a full build validation was not completed.

---

Codex Task

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.
To continue using code reviews, you can upgrade your account or add credits to your account and enable them for code reviews in your settings.