Add estimated tx fee to amount check when posting bid.

Add more log messages around balance checks.

basicswap/interface/xmr.py

@@ -71,6 +71,11 @@ class XMRInterface(CoinInterface):
     def xmr_swap_a_lock_spend_tx_vsize() -> int:
         raise ValueError("Not possible")
 
+    @staticmethod
+    def est_lock_tx_vsize() -> int:
+        # TODO: Estimate with ringsize
+        return 1604
+
     @staticmethod
     def xmr_swap_b_lock_spend_tx_vsize() -> int:
         # TODO: Estimate with ringsize