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

web/public/exchange-icons/gate.svg

@@ -0,0 +1,7 @@
+<svg viewBox="0 0 40 40" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <rect width="40" height="40" rx="8" fill="#1C1C28"/>
+  <g transform="translate(8, 8)">
+    <path d="M12 18.6c-3.64 0-6.6-2.96-6.6-6.6s2.96-6.6 6.6-6.6V0C5.37 0 0 5.38 0 12s5.37 12 12 12c6.62 0 12-5.38 12-12h-5.4c0 3.64-2.96 6.6-6.6 6.6z" fill="#2354e6"/>
+    <path d="M12 12h6.6V5.4H12z" fill="#17e6a1"/>
+  </g>
+</svg>

web/public/exchange-icons/kucoin.svg

@@ -0,0 +1,6 @@
+<svg viewBox="0 0 40 40" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <rect width="40" height="40" rx="8" fill="#1C1C28"/>
+  <g transform="translate(5, 5) scale(0.15)">
+    <path d="M57.7007 99.9146L116.94 159.158L154.381 121.714C160.964 115.131 171.734 115.131 178.317 121.714C184.899 128.297 184.899 139.068 178.317 145.651L128.908 195.063C122.326 201.646 111.555 201.646 104.973 195.063L34.0221 123.937V166.339C34.0221 175.572 26.4997 183.351 17.0111 183.351C7.52258 183.351 0 175.828 0 166.339V34.003C0 24.5138 7.52258 16.9908 17.0111 16.9908C26.4997 16.9908 34.0221 24.5138 34.0221 34.003V76.0633L105.143 4.93695C111.726 -1.64565 122.496 -1.64565 129.079 4.93695L178.488 54.3492C185.07 60.9318 185.07 71.7034 178.488 78.286C171.905 84.8686 161.135 84.8686 154.552 78.286L117.111 40.8421L57.7007 100.085V99.9146ZM117.111 82.9024C107.622 82.9024 100.1 90.4254 100.1 99.9146C100.1 109.404 107.622 116.927 117.111 116.927C126.6 116.927 134.122 109.404 134.122 99.9146C133.951 90.4254 126.429 82.9024 117.111 82.9024Z" fill="#00B47D"/>
+  </g>
+</svg>

web/src/components/ExchangeIcons.tsx

@@ -12,6 +12,7 @@ const ICON_PATHS: Record<string, string> = {
   bybit: '/exchange-icons/bybit.png',
   okx: '/exchange-icons/okx.svg',
   bitget: '/exchange-icons/bitget.svg',
+  gate: '/exchange-icons/gate.svg',
   kucoin: '/exchange-icons/kucoin.svg',
   hyperliquid: '/exchange-icons/hyperliquid.png',
   aster: '/exchange-icons/aster.svg',
@@ -90,15 +91,17 @@ export const getExchangeIcon = (
         ? 'okx'
         : lowerType.includes('bitget')
           ? 'bitget'
-          : lowerType.includes('kucoin')
-            ? 'kucoin'
-            : lowerType.includes('hyperliquid')
-              ? 'hyperliquid'
-              : lowerType.includes('aster')
-                ? 'aster'
-                : lowerType.includes('lighter')
-                  ? 'lighter'
-                  : lowerType
+          : lowerType.includes('gate')
+            ? 'gate'
+            : lowerType.includes('kucoin')
+              ? 'kucoin'
+              : lowerType.includes('hyperliquid')
+                ? 'hyperliquid'
+                : lowerType.includes('aster')
+                  ? 'aster'
+                  : lowerType.includes('lighter')
+                    ? 'lighter'
+                    : lowerType
 
   const iconProps = {
     width: props.width || 24,

web/src/components/traders/ExchangeConfigModal.tsx

@@ -25,6 +25,7 @@ const SUPPORTED_EXCHANGE_TEMPLATES = [
   { exchange_type: 'bybit', name: 'Bybit Futures', type: 'cex' as const },
   { exchange_type: 'okx', name: 'OKX Futures', type: 'cex' as const },
   { exchange_type: 'bitget', name: 'Bitget Futures', type: 'cex' as const },
+  { exchange_type: 'gate', name: 'Gate.io Futures', type: 'cex' as const },
   { exchange_type: 'kucoin', name: 'KuCoin Futures', type: 'cex' as const },
   { exchange_type: 'hyperliquid', name: 'Hyperliquid', type: 'dex' as const },
   { exchange_type: 'aster', name: 'Aster DEX', type: 'dex' as const },
@@ -198,6 +199,7 @@ export function ExchangeConfigModal({
     okx: { url: 'https://www.okx.com/join/1865360', hasReferral: true },
     bybit: { url: 'https://partner.bybit.com/b/83856', hasReferral: true },
     bitget: { url: 'https://www.bitget.com/referral/register?from=referral&clacCode=c8a43172', hasReferral: true },
+    gate: { url: 'https://www.gatenode.xyz/share/VQBGUAxY', hasReferral: true },
     kucoin: { url: 'https://www.kucoin.com/r/broker/CXEV7XKK', hasReferral: true },
     hyperliquid: { url: 'https://app.hyperliquid.xyz/join/AITRADING', hasReferral: true },
     aster: { url: 'https://www.asterdex.com/en/referral/fdfc0e', hasReferral: true },
@@ -501,7 +503,7 @@ export function ExchangeConfigModal({
               </div>
 
               {/* CEX Fields */}
-              {(currentExchangeType === 'binance' || currentExchangeType === 'bybit' || currentExchangeType === 'okx' || currentExchangeType === 'bitget' || currentExchangeType === 'kucoin') && (
+              {(currentExchangeType === 'binance' || currentExchangeType === 'bybit' || currentExchangeType === 'okx' || currentExchangeType === 'bitget' || currentExchangeType === 'gate' || currentExchangeType === 'kucoin') && (
                 <>
                   {currentExchangeType === 'binance' && (
                     <div