feat: Add Hyperliquid exchange support with unified trader interface

Major changes:
- Add full Hyperliquid trading support (long/short, leverage, SL/TP)
- Create unified Trader interface for multi-exchange support
- Implement automatic precision handling for orders and prices
- Fix balance calculation and unrealized P&L display
- Add comprehensive configuration guide in README

New features:
- Support for both Binance and Hyperliquid exchanges
- Automatic order size precision based on szDecimals
- Price formatting with 5 significant figures
- Non-custodial trading with Ethereum private key
- Seamless exchange switching via configuration

Technical details:
- Add trader/interface.go for unified trader interface
- Add trader/hyperliquid_trader.go for Hyperliquid implementation
- Update manager and auto_trader to support multiple exchanges
- Add go-hyperliquid SDK dependency
- Fix precision errors (float_to_wire, invalid price)

Fixes:
- Correct calculation of wallet balance and unrealized P&L
- Proper handling of AccountValue vs TotalRawUsd
- Frontend display issues for total equity and P&L

Documentation:
- Add Hyperliquid setup guide in README
- Update config.json.example with both exchanges
- Add troubleshooting section for common errors

Tested with live trading on Hyperliquid mainnet.
No breaking changes - backward compatible with existing configs.

config.json.example

@@ -1,15 +1,25 @@
 {
   "traders": [
     {
-      "id": "my_trader",
-      "name": "My AI Trader",
+      "id": "hyperliquid_deepseek",
+      "name": "Hyperliquid DeepSeek Trader",
       "ai_model": "deepseek",
-      "binance_api_key": "YOUR_BINANCE_API_KEY",
-      "binance_secret_key": "YOUR_BINANCE_SECRET_KEY",
-      "use_qwen": false,
-      "deepseek_key": "YOUR_DEEPSEEK_API_KEY",
-      "qwen_key": "",
-      "initial_balance": 1000.0,
+      "exchange": "hyperliquid",
+      "hyperliquid_private_key": "your_ethereum_private_key_without_0x_prefix",
+      "hyperliquid_testnet": false,
+      "deepseek_key": "your_deepseek_api_key",
+      "initial_balance": 1000,
+      "scan_interval_minutes": 3
+    },
+    {
+      "id": "binance_qwen",
+      "name": "Binance Qwen Trader",
+      "ai_model": "qwen",
+      "exchange": "binance",
+      "binance_api_key": "your_binance_api_key",
+      "binance_secret_key": "your_binance_secret_key",
+      "qwen_key": "your_qwen_api_key",
+      "initial_balance": 1000,
       "scan_interval_minutes": 3
     }
   ],
@@ -17,7 +27,7 @@
   "coin_pool_api_url": "",
   "oi_top_api_url": "",
   "api_server_port": 8080,
-  "max_daily_loss": 5.0,
-  "max_drawdown": 10.0,
-  "stop_trading_minutes": 30
+  "max_daily_loss": 10.0,
+  "max_drawdown": 20.0,
+  "stop_trading_minutes": 60
 }