feat: fix Lighter V2 integration and improve error handling

- Fix Lighter API field name mismatches (position/size, avg_entry_price/entry_price, sign/side)
- Fix GetBalance return format to match standard fields (totalWalletBalance, totalUnrealizedProfit)
- Fix GetPositions return format to match standard fields (positionAmt, markPrice, unRealizedProfit)
- Add API Key Index field to frontend with explanation
- Update Lighter referral link
- Disable Lighter testnet (mainnet only)
- Add load error tracking for better error messages
- Remove old Lighter V1 implementation files
- Remove test credentials from test files

web/src/components/TraderConfigModal.tsx

@@ -19,7 +19,7 @@ const EXCHANGE_REGISTRATION_LINKS: Record<string, { url: string; hasReferral?: b
   bybit: { url: 'https://partner.bybit.com/b/83856', hasReferral: true },
   hyperliquid: { url: 'https://app.hyperliquid.xyz/join/AITRADING', hasReferral: true },
   aster: { url: 'https://www.asterdex.com/en/referral/fdfc0e', hasReferral: true },
-  lighter: { url: 'https://lighter.xyz', hasReferral: false },
+  lighter: { url: 'https://app.lighter.xyz/?referral=68151432', hasReferral: true },
 }
 
 import type { TraderConfigData } from '../types'