fix: Correct BN import for withdrawal system

Changed from '@project-serum/anchor' to 'bn.js' to match
other Drift SDK integrations. Fixes 'Cannot read properties
of undefined (reading '_bn')' error.

User can now test withdrawal with $5 minimum.

.env

@@ -412,4 +412,11 @@ TRAILING_STOP_MAX_PERCENT=2.5
 USE_PERCENTAGE_SIZE=false
 
 BREAKEVEN_TRIGGER_PERCENT=0.4
-ATR_MULTIPLIER_FOR_TP2=2
+ATR_MULTIPLIER_FOR_TP2=2
+ENABLE_AUTO_WITHDRAWALS=false
+WITHDRAWAL_INTERVAL_HOURS=168
+WITHDRAWAL_PROFIT_PERCENT=10
+MIN_WITHDRAWAL_AMOUNT=5
+MIN_ACCOUNT_BALANCE=500
+LAST_WITHDRAWAL_TIME=
+TOTAL_WITHDRAWN=0