refactor: remove all Debate Arena feature code

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.

web/src/types.ts

@@ -616,123 +616,6 @@ export interface RiskControlConfig {
   min_confidence: number;          // Min AI confidence to open position (AI guided)
 }
 
-// Debate Arena Types
-export type DebateStatus = 'pending' | 'running' | 'voting' | 'completed' | 'cancelled';
-export type DebatePersonality = 'bull' | 'bear' | 'analyst' | 'contrarian' | 'risk_manager';
-
-export interface DebateDecision {
-  action: string;
-  symbol: string;
-  confidence: number;
-  leverage?: number;
-  position_pct?: number;
-  position_size_usd?: number;
-  stop_loss?: number;
-  take_profit?: number;
-  reasoning: string;
-  // Execution tracking
-  executed?: boolean;
-  executed_at?: string;
-  order_id?: string;
-  error?: string;
-}
-
-export interface DebateSession {
-  id: string;
-  user_id: string;
-  name: string;
-  strategy_id: string;
-  status: DebateStatus;
-  symbol: string;
-  interval_minutes: number;
-  prompt_variant: string;
-  trader_id?: string;
-  max_rounds: number;
-  current_round: number;
-  final_decision?: DebateDecision;
-  final_decisions?: DebateDecision[];  // Multi-coin decisions
-  auto_execute: boolean;
-  created_at: string;
-  updated_at: string;
-}
-
-export interface DebateParticipant {
-  id: string;
-  session_id: string;
-  ai_model_id: string;
-  ai_model_name: string;
-  provider: string;
-  personality: DebatePersonality;
-  color: string;
-  speak_order: number;
-  created_at: string;
-}
-
-export interface DebateMessage {
-  id: string;
-  session_id: string;
-  round: number;
-  ai_model_id: string;
-  ai_model_name: string;
-  provider: string;
-  personality: DebatePersonality;
-  message_type: string;
-  content: string;
-  decision?: DebateDecision;
-  decisions?: DebateDecision[];  // Multi-coin decisions
-  confidence: number;
-  created_at: string;
-}
-
-export interface DebateVote {
-  id: string;
-  session_id: string;
-  ai_model_id: string;
-  ai_model_name: string;
-  action: string;
-  symbol: string;
-  confidence: number;
-  leverage?: number;
-  position_pct?: number;
-  stop_loss_pct?: number;
-  take_profit_pct?: number;
-  reasoning: string;
-  created_at: string;
-}
-
-export interface DebateSessionWithDetails extends DebateSession {
-  participants: DebateParticipant[];
-  messages: DebateMessage[];
-  votes: DebateVote[];
-}
-
-export interface CreateDebateRequest {
-  name: string;
-  strategy_id: string;
-  symbol: string;
-  max_rounds?: number;
-  interval_minutes?: number;  // 5, 15, 30, 60 minutes
-  prompt_variant?: string;    // balanced, aggressive, conservative, scalping
-  auto_execute?: boolean;
-  trader_id?: string;         // Trader to use for auto-execute
-  // OI Ranking data options
-  enable_oi_ranking?: boolean;  // Whether to include OI ranking data
-  oi_ranking_limit?: number;    // Number of OI ranking entries (default 10)
-  oi_duration?: string;         // Duration for OI data (1h, 4h, 24h, etc.)
-  participants: {
-    ai_model_id: string;
-    personality: DebatePersonality;
-  }[];
-}
-
-export interface DebatePersonalityInfo {
-  id: DebatePersonality;
-  name: string;
-  emoji: string;
-  color: string;
-  description: string;
-}
-
 // Position History Types
 export interface HistoricalPosition {
   id: number;