Add better fee error handling and monitoring

- Log clear error messages when fee buffer is too low
- Show exact shortfall amount and required action
- Add DOGE_REFUND_FEE_BUFFER environment variable for dynamic adjustment
- Log actual fee buffer used on successful refunds
- Add helpful comment in vars.sh about the fee buffer setting

Now when watching crypto-watcher logs, admins will see:
- 'INSUFFICIENT FUNDS - Fee estimate too low\!'
- Current buffer, shortfall amount, and line number to fix
- Success messages show actual vs estimated fee usage

This makes it much easier to adjust the fee buffer without diving into code.

make_post_sell/lib/crypto_watcher/crypto_payment_rescue.py

@@ -294,7 +294,11 @@ class PaymentRescue:
                 # Account for network fee by reducing amounts proportionally
                 # Dogecoin sendmany adds fee on top of outputs, so we need to leave room
                 total_output = refund_amount_doge + shop_amount_doge
-                estimated_fee = 0.005  # Reasonable fee for 1-input, 2-output transaction
+                
+                # Fee estimate - can be overridden via environment variable
+                import os
+                estimated_fee = float(os.environ.get('DOGE_REFUND_FEE_BUFFER', '0.005'))
+                logger.debug(f"Using fee buffer: {estimated_fee} DOGE")
                 
                 # Check if we need to adjust for fees
                 if balance_result and total_output + estimated_fee > balance_result:
@@ -329,13 +333,34 @@ class PaymentRescue:
                 try:
                     tx_hash = self.crypto_client.sendmany(from_account, clean_outputs, 1)
                 except Exception as e:
-                    # If that fails, try with empty account (default)
-                    if "insufficient funds" in str(e).lower():
-                        tx_hash = self.crypto_client.sendmany("", clean_outputs, 1)
+                    error_msg = str(e).lower()
+                    if "insufficient funds" in error_msg:
+                        # Log detailed fee information when we hit insufficient funds
+                        logger.error(f"INSUFFICIENT FUNDS - Fee estimate too low!")
+                        logger.error(f"Current fee buffer: {estimated_fee} DOGE")
+                        logger.error(f"Total outputs: {sum(clean_outputs.values())} DOGE")
+                        logger.error(f"Available balance: {balance_result} DOGE")
+                        shortfall = sum(clean_outputs.values()) + estimated_fee - balance_result
+                        logger.error(f"Shortfall: {shortfall:.8f} DOGE (may need more for actual network fee)")
+                        logger.error(f"ACTION REQUIRED: Increase estimated_fee in crypto_payment_rescue.py line ~318")
+                        
+                        # Try with default account as fallback
+                        try:
+                            tx_hash = self.crypto_client.sendmany("", clean_outputs, 1)
+                        except Exception as e2:
+                            if "insufficient funds" in str(e2).lower():
+                                logger.error(f"Both accounts failed - fee definitely too low!")
+                            raise e2
                     else:
                         raise
                 
                 tx_result = {"tx_hash": tx_hash}
+                
+                # Log success with fee info for monitoring
+                logger.info(f"Refund sent successfully! TX: {tx_hash}")
+                if balance_result:
+                    buffer_used = balance_result - sum(clean_outputs.values())
+                    logger.info(f"Fee buffer used: {buffer_used:.8f} DOGE (estimated: {estimated_fee})")
 
             else:
                 raise ValueError(f"Refund not supported for coin type: {coin_type}")