Remove the entire AI Debate Arena module (~5,300 lines) to simplify
the codebase. This removes the multi-AI debate trading decision system
including backend engine, API handlers, database store, frontend page,
navigation, translations, and documentation references.
- Add HeaderBar to FAQ page for proper navigation
- Rewrite FAQ with 9 categories and ~50 Q&A items
- Add EN/ZH translations for all FAQ content
- Remove China-specific references
- Update AI model names (GPT-5.2)
- Update description to include crypto and US stock markets