- VitalGauge.tsx: New component with:
- SVG sparkline charts showing historical trend
- Gradient fill under sparkline
- Trend arrows (up/down/stable)
- Pulsing current value dot
- Hover tooltips with optimal/range info
- Color-coded status (green/yellow/red)
- VitalsGrid: Convenient wrapper for common vitals
- VitalGaugeMini: Compact version for lists
- Consistent mock values per plant (seeded by ID)
