Add charts for sites/functions usage

[hmacr]

Task: https://linear.app/appwrite/issue/SER-476/add-charts-for-sitesfunctions-usage

Summary by CodeRabbit

• New Features

  • Bandwidth visualization with bar charts added to usage pages
  • GB-hours consumption tracking added alongside execution metrics
  • Empty-state UI with icon and “No data to show” message when no data

• Improvements

  • Consistent executions-focused metrics across usage views (titles/legends updated)
  • Human-readable formatting for bandwidth totals and chart labels
  • GB-hours shown as a secondary Usage block (period selector hidden)
  • Total value and its label now aligned horizontally for clearer display