feat(gate): complete Gate.io exchange integration with trader refactoring

Gate.io Integration:
- Add Gate trader with full Trader interface implementation
- Add order_sync.go for background trade synchronization
- Fix quantity display (convert contracts to actual tokens via quanto_multiplier)
- Fix fill price return in OpenLong/OpenShort/CloseLong/CloseShort
- Add Gate-specific CoinAnk K-line data source support
- Add Gate to supported exchanges in frontend and backend
- Add Gate/KuCoin logo SVG icons

Trader Package Refactoring:
- Move exchange-specific code into subdirectories (binance/, bybit/, okx/, bitget/, hyperliquid/, aster/, lighter/, gate/)
- Create types/ package for shared types to avoid circular dependencies
- Move TraderTestSuite to trader/testutil package to avoid import cycles
- Update market.GetWithExchange to support exchange-specific data

README.md

@@ -38,7 +38,7 @@
 ### Core Features
 
 - **Multi-AI Support**: Run DeepSeek, Qwen, GPT, Claude, Gemini, Grok, Kimi - switch models anytime
-- **Multi-Exchange**: Trade on Binance, Bybit, OKX, Bitget, Hyperliquid, Aster DEX, Lighter from one platform
+- **Multi-Exchange**: Trade on Binance, Bybit, OKX, Bitget, KuCoin, Gate, Hyperliquid, Aster DEX, Lighter from one platform
 - **Strategy Studio**: Visual strategy builder with coin sources, indicators, and risk controls
 - **AI Debate Arena**: Multiple AI models debate trading decisions with different roles (Bull, Bear, Analyst)
 - **AI Competition Mode**: Multiple AI traders compete in real-time, track performance side by side
@@ -84,6 +84,7 @@ To use NOFX, you'll need:
 | **OKX** | ✅ Supported | [Register](https://www.okx.com/join/1865360) |
 | **Bitget** | ✅ Supported | [Register](https://www.bitget.com/referral/register?from=referral&clacCode=c8a43172) |
 | **KuCoin** | ✅ Supported | [Register](https://www.kucoin.com/r/broker/CXEV7XKK) |
+| **Gate** | ✅ Supported | [Register](https://www.gatenode.xyz/share/VQBGUAxY) |
 
 ### Perp-DEX (Decentralized Perpetual Exchanges)