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/thinking/engine.go

@@ -0,0 +1,28 @@
+package thinking
+
+import "context"
+
+// Engine is the AI decision-making interface.
+type Engine interface {
+	// Chat sends a message to the LLM with conversation context and returns a response.
+	Chat(ctx context.Context, messages []Message) (string, error)
+
+	// Analyze asks the AI to analyze market data and provide a trading recommendation.
+	Analyze(ctx context.Context, prompt string) (*Analysis, error)
+}
+
+// Message represents a chat message.
+type Message struct {
+	Role    string `json:"role"`    // "system", "user", "assistant"
+	Content string `json:"content"`
+}
+
+// Analysis holds an AI trading recommendation.
+type Analysis struct {
+	Action     string  `json:"action"`      // "buy", "sell", "hold", "wait"
+	Symbol     string  `json:"symbol"`
+	Confidence float64 `json:"confidence"`  // 0.0 - 1.0
+	Reasoning  string  `json:"reasoning"`
+	StopLoss   float64 `json:"stop_loss,omitempty"`
+	TakeProfit float64 `json:"take_profit,omitempty"`
+}