feat(hyperliquid): Auto-generate wallet address from private key

Enable automatic wallet address generation from private key for Hyperliquid
exchange, simplifying user onboarding and reducing configuration errors.

Backend Changes (trader/hyperliquid_trader.go):
- Import crypto/ecdsa package for ECDSA public key operations
- Enable wallet address auto-generation when walletAddr is empty
- Use crypto.PubkeyToAddress() to derive address from private key
- Add logging for both auto-generated and manually provided addresses

Frontend Changes (web/src/components/AITradersPage.tsx):
- Remove wallet address required validation (only private key required)
- Update button disabled state to only check private key
- Add "Optional" label to wallet address field
- Add dynamic placeholder with bilingual hint
- Show context-aware helper text based on input state
- Remove HTML required attribute from input field

Translation Updates (web/src/i18n/translations.ts):
- Add 'optional' translation (EN: "Optional", ZH: "可选")
- Add 'hyperliquidWalletAddressAutoGenerate' translation
  EN: "Leave blank to automatically generate wallet address from private key"
  ZH: "留空将自动从私钥生成钱包地址"

Benefits:
✅ Simplified UX - Users only need to provide private key
✅ Error prevention - Auto-generated address always matches private key
✅ Backward compatible - Manual address input still supported
✅ Better UX - Clear visual indicators for optional fields

Technical Details:
- Uses Ethereum standard ECDSA public key to address conversion
- Implementation was already present but commented out (lines 37-43)
- No database schema changes required (hyperliquid_wallet_addr already nullable)
- Fallback behavior: manual input > auto-generation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

trader/hyperliquid_trader.go

@@ -2,6 +2,7 @@ package trader
 
 import (
 	"context"
+	"crypto/ecdsa"
 	"encoding/json"
 	"fmt"
 	"log"
@@ -34,13 +35,18 @@ func NewHyperliquidTrader(privateKeyHex string, walletAddr string, testnet bool)
 		apiURL = hyperliquid.TestnetAPIURL
 	}
 
-	// // 从私钥生成钱包地址
-	// pubKey := privateKey.Public()
-	// publicKeyECDSA, ok := pubKey.(*ecdsa.PublicKey)
-	// if !ok {
-	// 	return nil, fmt.Errorf("无法转换公钥")
-	// }
-	// walletAddr := crypto.PubkeyToAddress(*publicKeyECDSA).Hex()
+	// 从私钥生成钱包地址（如果未提供）
+	if walletAddr == "" {
+		pubKey := privateKey.Public()
+		publicKeyECDSA, ok := pubKey.(*ecdsa.PublicKey)
+		if !ok {
+			return nil, fmt.Errorf("无法转换公钥")
+		}
+		walletAddr = crypto.PubkeyToAddress(*publicKeyECDSA).Hex()
+		log.Printf("✓ 从私钥自动生成钱包地址: %s", walletAddr)
+	} else {
+		log.Printf("✓ 使用提供的钱包地址: %s", walletAddr)
+	}
 
 	ctx := context.Background()