Description:

Resolves #5
Resolves #6

This PR fixes the broken local Docker environment, allowing new contributors to successfully run docker-compose up --build as outlined in the contributing guidelines. It also resolves the 413 Body exceeded 1 MB limit crash that occurs when uploading real-world ASL datasets.

1. Build Fixes (Node 20 & ESLint):

• Bumped node:18-alpine to node:20-alpine in apps/frontend/Dockerfile to satisfy updated dependency engine requirements.
• Removed unused variables and explicitly cast .length to Number() in UploadButtons.tsx to pass strict ESLint/TypeScript checks.
• Handled legacy any types in uploadHandlers.ts to unblock the Next.js production build.

2. Large Payload Upload Fix:

• Explicitly set bodySizeLimit: '100mb' in next.config.ts to allow large DICOM/NIfTI folder uploads.
• Added COPY --from=builder /app/next.config.ts ./ to the runner stage of the Dockerfile to ensure the 100MB limit is actually applied in the production image.
• Instead of requiring developers to manually create a .env.local file, I configured Next.js rewrites to proxy /api traffic directly to the internal Docker backend network.
• This provides a true zero-configuration deployment that automatically resolves the 404 routing errors for all new contributors out-of-the-box.

Pull Request Review Checklist

• Code follows style guidelines
• Tests are included and passing (Tested manually end-to-end with real BIDS data)
• Documentation is updated (No docs changes required)
• No breaking changes (or properly documented)
• Error handling is appropriate
• Performance considerations addressed
• Security Implications considered (Next.js 100MB limit is scoped only to required Server Actions)