Add first-run onboarding flow for new journals
When a journal has no facets, redirect root to settings where an inline
"Welcome" section offers one-click creation of a Personal facet (🏠, blue).
Home app also shows a friendly empty state pointing to settings.
- Root route checks for facets, redirects to settings if empty
- Settings shows setup section when no facets exist
- create_facet API now accepts optional emoji and color params
- Home displays welcome message with link to settings when no facets
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>