DO NOT MERGE: Add configurable course base domain and container support

[lgriffin]

DO NOT MERGE — Testing/Experimental

This PR is a proof of concept for deploying Tutors on Kubernetes/OpenShift. Not ready for production.

Summary

• Replace hardcoded .netlify.app domain in course URL resolution with a configurable PUBLIC_COURSE_BASE_DOMAIN environment variable (defaults to .netlify.app for backward compatibility)
• Add Dockerfile for building the reader as a Node.js container (multi-stage build using adapter-node)
• Add Dockerfile.course as a sample nginx container for serving static course content with CORS headers
• Add svelte.config.node.js so container builds use adapter-node while the repo default stays adapter-auto (Netlify unaffected)

Architecture

Approach 1: Reader deployed centrally on OpenShift, courses served from configurable locations (other containers, student machines, or existing Netlify sites).

Student machine                    OpenShift cluster
┌─────────────────┐               ┌──────────────────┐
│ Course container │◄──fetch──────│  Reader (SvelteKit)│
│ (nginx, :8080)  │   tutors.json │  (node, :3000)    │
└─────────────────┘               └──────────────────┘

Files changed

File	Change
src/lib/services/course/config.ts	New — centralizes PUBLIC_COURSE_BASE_DOMAIN with fallback
src/lib/services/course/services/lo-tree.ts	determineCourseUrl() accepts optional baseDomain param
src/lib/services/community/services/catalogue.ts	Uses configurable domain for catalogue pruning
.env.example	Documents PUBLIC_COURSE_BASE_DOMAIN
Dockerfile	Multi-stage reader container
Dockerfile.course	Sample course container (nginx + CORS)
svelte.config.node.js	adapter-node config for container builds
.dockerignore	Build context exclusions
vitest.config.ts	Alias for $env/static/public in tests
tests/mocks/env-static-public.ts	Mock env vars for test runner

Test plan

• All existing determineCourseUrl() tests pass (backward compatible)
• New configurable domain tests pass (7/7)
• npm run build succeeds
• Docker build and run the reader container
• Docker build and run a course container
• Verify reader fetches course from custom domain

🤖 Generated with Claude Code

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