feat: Add Aster DEX exchange support + fix precision issues

## Features
- Add full Aster DEX integration with Binance-compatible API
- Support Web3 authentication with API wallet system
- Add comprehensive Aster integration guide (ASTER_INTEGRATION.md)
- Add example Aster configuration (config.aster.example.json)

## Bug Fixes
- Fix precision error (code -1111) for all order types
- Implement proper float-to-string conversion with exchange precision
- Add automatic precision fetching from /exchangeInfo endpoint
- Remove trailing zeros from formatted values

## Documentation
- Update README.md with Aster quick start guide
- Add detailed setup instructions for creating API wallet
- Include troubleshooting FAQ and security best practices
- Update core features to mention three supported exchanges

## Technical Details
- Added formatFloatWithPrecision() helper function
- Updated all order functions to use proper precision formatting
- Added precision logging for debugging
- Fully backward compatible with existing configurations

Closes #[issue number if applicable]

config/config.go

@@ -24,6 +24,11 @@ type TraderConfig struct {
 	HyperliquidPrivateKey string `json:"hyperliquid_private_key,omitempty"`
 	HyperliquidTestnet    bool   `json:"hyperliquid_testnet,omitempty"`
 
+	// Aster配置
+	AsterUser       string `json:"aster_user,omitempty"`        // Aster主钱包地址
+	AsterSigner     string `json:"aster_signer,omitempty"`      // Aster API钱包地址
+	AsterPrivateKey string `json:"aster_private_key,omitempty"` // Aster API钱包私钥
+
 	// AI配置
 	QwenKey             string  `json:"qwen_key,omitempty"`
 	DeepSeekKey         string  `json:"deepseek_key,omitempty"`
@@ -108,8 +113,8 @@ func (c *Config) Validate() error {
 		if trader.Exchange == "" {
 			trader.Exchange = "binance" // 默认使用币安
 		}
-		if trader.Exchange != "binance" && trader.Exchange != "hyperliquid" {
-			return fmt.Errorf("trader[%d]: exchange必须是 'binance' 或 'hyperliquid'", i)
+		if trader.Exchange != "binance" && trader.Exchange != "hyperliquid" && trader.Exchange != "aster" {
+			return fmt.Errorf("trader[%d]: exchange必须是 'binance', 'hyperliquid' 或 'aster'", i)
 		}
 
 		// 根据平台验证对应的密钥
@@ -121,6 +126,10 @@ func (c *Config) Validate() error {
 			if trader.HyperliquidPrivateKey == "" {
 				return fmt.Errorf("trader[%d]: 使用Hyperliquid时必须配置hyperliquid_private_key", i)
 			}
+		} else if trader.Exchange == "aster" {
+			if trader.AsterUser == "" || trader.AsterSigner == "" || trader.AsterPrivateKey == "" {
+				return fmt.Errorf("trader[%d]: 使用Aster时必须配置aster_user, aster_signer和aster_private_key", i)
+			}
 		}
 
 		if trader.AIModel == "qwen" && trader.QwenKey == "" {