feat(web): add desc display option to sort tooltip items descending

[ducthotran2010]

• Add desc field to ChartDisplay in web/config.go to configure tooltip sort order
• Regenerate web/src/generated.ts to include desc: boolean in ChartDisplay
• When display.desc: true, render a custom ApexCharts tooltip that sorts series items by value highest → lowest

Usage

charts:
  - name: My Chart
    display:
      desc: true