add justfile for dev workflows and SvelteKit frontend prep
- created justfile with common dev commands for both backend and frontend
- organized commands into groups (backend, frontend, database, development)
- includes recipes for: serve, dev, lint, format, check, test, build, etc.
- cloned HuggingChat (huggingface/chat-ui) to sandbox as SvelteKit reference
- updated CLAUDE.md with SvelteKit frontend notes and justfile usage
ready to scaffold SvelteKit frontend next.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>