## Why

The existing Dockerfile is configured for Angular's build output (`/dist/hosting-frontend/browser`), which is incompatible with the Next.js migration. Next.js with `output: 'standalone'` generates a different directory structure and requires a multi-stage Docker build to minimize image size while maintaining production performance.

This proposal updates the Dockerfile to support Next.js 15's standalone output mode, enabling efficient production deployments with reduced image size and faster cold starts.

## What Changes

- **Update Dockerfile**: Replace Angular build path with Next.js standalone output
- **Add multi-stage build**: Separate build stage from runtime stage to reduce final image size
- **Configure production runtime**: Use Node.js runtime instead of nginx
- **Add .dockerignore**: Exclude development files and dependencies from the Docker context
- **Environment variable support**: Ensure build and runtime environment variables are properly handled

## Impact

- **Affected specs**: `deployment`, `build-process`
- **Affected code**:
  - `Dockerfile` (primary)
  - `.dockerignore` (new)
  - Build scripts in CI/CD pipelines
- **Breaking changes**: None (this completes the migration already started)
- **Migration path**: Update Docker image build commands; no application code changes needed

## Risk Mitigation

- Multi-stage build ensures small image size (~150-200MB vs ~500MB+ with development dependencies)
- Standalone mode eliminates need for separate node_modules in production
- Nginx is replaced with Next.js native HTTP server (built-in performance optimization)
- Image runs as non-root user for security best practices