[UST-227] [Frontend] Add Platform Policy page, detailing the mechanisms for reporting, adjudication, and reputation

[Xiawpohr]

Is your feature request related to a problem? Please describe. Provide more information about this website and services to let users understand what the product is and how it works.

Describe the solution you'd like

• Remove the explore page
• Add Page::About that contains these sections
  • 平台特點與機制介紹
  • 平台政策
  • 開源資訊與 Discord 社群
  • 常見問題

Additional context Figma

Related issue

529

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Story point: 3 Reporter: @Xiawpohr