fix(hud): fix Decimal/float division error in cost calculation

- Convert both damage and dpp to Decimal before division
- Proper Decimal arithmetic for precision

ui/main_window.py

@@ -1008,13 +1008,16 @@ class MainWindow(QMainWindow):
             
             # Estimate cost per shot based on weapon stats
             if self._selected_weapon_stats:
-                # Rough estimate: if we know DPP and damage, we can estimate cost
                 dpp = self._selected_weapon_stats.get('dpp', 0)
-                if dpp > 0:
+                if dpp and dpp > 0:
                     # Cost per shot in PEC = damage / DPP
-                    cost_pec = damage / dpp
-                    cost_ped = cost_pec / 100  # Convert to PED
-                    self.hud.update_cost(Decimal(str(cost_ped)))
+                    # Convert to Decimal for precision
+                    from decimal import Decimal
+                    damage_dec = Decimal(str(damage))
+                    dpp_dec = Decimal(str(dpp))
+                    cost_pec = damage_dec / dpp_dec
+                    cost_ped = cost_pec / Decimal('100')  # Convert to PED
+                    self.hud.update_cost(cost_ped)
         
         def on_critical_hit(event):
             """Handle critical hit - same as damage dealt."""