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/types.ts

@@ -131,6 +131,7 @@ export interface Exchange {
   lighterWalletAddr?: string
   lighterPrivateKey?: string
   lighterApiKeyPrivateKey?: string
+  lighterApiKeyIndex?: number
 }
 
 export interface CreateExchangeRequest {
@@ -148,6 +149,7 @@ export interface CreateExchangeRequest {
   lighter_wallet_addr?: string
   lighter_private_key?: string
   lighter_api_key_private_key?: string
+  lighter_api_key_index?: number
 }
 
 export interface CreateTraderRequest {
@@ -199,6 +201,7 @@ export interface UpdateExchangeConfigRequest {
       lighter_wallet_addr?: string
       lighter_private_key?: string
       lighter_api_key_private_key?: string
+      lighter_api_key_index?: number
     }
   }
 }