fix: TypeScript errors in withdrawal system

- Fixed LAST_WITHDRAWAL_TIME type (null | string)
- Removed parseFloat on health.freeCollateral (already number)
- Fixed getDriftClient() → getClient() method name
- Build now compiles successfully

Deployed: Withdrawal system now live on dashboard

app/api/withdrawals/settings/route.ts

@@ -19,7 +19,7 @@ const DEFAULT_SETTINGS = {
   MIN_WITHDRAWAL_AMOUNT: 50, // Minimum $50
   MIN_ACCOUNT_BALANCE: 500, // Never drop below $500
   WITHDRAWAL_DESTINATION: process.env.WALLET_PUBLIC_KEY || '',
-  LAST_WITHDRAWAL_TIME: null,
+  LAST_WITHDRAWAL_TIME: null as string | null,
   TOTAL_WITHDRAWN: 0,
 }