feat: init nofxi - AI Trading Agent module

NOFXi — Your AI Trading Agent, built on NOFX.

Architecture:
- Agent Core: intent routing, conversation memory, trade confirmation
- Memory: SQLite (trades, conversations, preferences, strategies)
- Thinking: LLM client (OpenAI/claw402/DeepSeek compatible)
- Execution: Bridge to NOFX trader engine (9 exchanges)
- Perception: Market monitor, price alerts, anomaly detection
- Interaction: Telegram bot + REST API + OpenAI-compatible endpoint

Features:
- Natural language trading (中英文)
- /buy /sell /analyze /watch /alert /positions /balance
- Daily P/L reports, portfolio risk checks
- Trade confirmation flow (safety first)
- Price polling and alert notifications

nofxi/internal/memory/models.go

@@ -0,0 +1,64 @@
+package memory
+
+import "time"
+
+// TradeRecord stores a completed or active trade.
+type TradeRecord struct {
+	ID         int64     `json:"id"`
+	Exchange   string    `json:"exchange"`
+	Symbol     string    `json:"symbol"`
+	Side       string    `json:"side"`       // "buy" or "sell"
+	Type       string    `json:"type"`       // "market", "limit"
+	Price      float64   `json:"price"`
+	Quantity   float64   `json:"quantity"`
+	PnL        float64   `json:"pnl"`        // Realized P/L
+	Fee        float64   `json:"fee"`
+	Status     string    `json:"status"`     // "open", "closed", "cancelled"
+	AIModel    string    `json:"ai_model"`   // Which AI model made the decision
+	AIReason   string    `json:"ai_reason"`  // Why AI made this decision
+	StrategyID string    `json:"strategy_id"`
+	CreatedAt  time.Time `json:"created_at"`
+	ClosedAt   *time.Time `json:"closed_at,omitempty"`
+}
+
+// UserPreference stores user settings and preferences.
+type UserPreference struct {
+	ID        int64     `json:"id"`
+	UserID    int64     `json:"user_id"`    // Telegram user ID
+	Key       string    `json:"key"`
+	Value     string    `json:"value"`
+	UpdatedAt time.Time `json:"updated_at"`
+}
+
+// Conversation stores chat messages for context.
+type Conversation struct {
+	ID        int64     `json:"id"`
+	UserID    int64     `json:"user_id"`
+	Role      string    `json:"role"`       // "user", "assistant", "system"
+	Content   string    `json:"content"`
+	CreatedAt time.Time `json:"created_at"`
+}
+
+// StrategyPerformance tracks how well a strategy has performed.
+type StrategyPerformance struct {
+	ID           int64     `json:"id"`
+	StrategyID   string    `json:"strategy_id"`
+	StrategyName string    `json:"strategy_name"`
+	TotalTrades  int       `json:"total_trades"`
+	WinRate      float64   `json:"win_rate"`
+	TotalPnL     float64   `json:"total_pnl"`
+	MaxDrawdown  float64   `json:"max_drawdown"`
+	SharpeRatio  float64   `json:"sharpe_ratio"`
+	UpdatedAt    time.Time `json:"updated_at"`
+}
+
+// MarketSnapshot stores a point-in-time market state for pattern recognition.
+type MarketSnapshot struct {
+	ID        int64     `json:"id"`
+	Symbol    string    `json:"symbol"`
+	Price     float64   `json:"price"`
+	Volume24h float64   `json:"volume_24h"`
+	Change24h float64   `json:"change_24h"`
+	Note      string    `json:"note"`       // AI observation about this snapshot
+	CreatedAt time.Time `json:"created_at"`
+}