Complete visual overhaul matching Month view style:
- GitHub-style heatmap grid (12 columns for months, days as rows)
- Donut chart showing mood distribution with total days in center
- Bar chart stats alongside donut chart
- Collapsible stats section with chevron toggle
- YearCard, YearHeatmapGrid, MonthColumn, YearHeatmapCell components
- Consistent styling with Month view redesign
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
