feat: add notification for buildings sold due to insufficient gold

Handle 'buildingSold' events to inform players when their buildings are
automatically sold to cover upkeep costs, displaying the building name
and city where the sale occurred.

src/games/civilization/CivilizationGame.js

@@ -1483,6 +1483,11 @@ export default class CivilizationGame extends Phaser.Scene {
               });
             },
           });
+      } else if (e.type === 'buildingSold' && e.civ === human) {
+        const city = Logic.cityById(this.state, e.cityId);
+        const building = this.rules.buildings[e.building];
+        if (!city || !building) continue;
+        this.announceStatus(`Not enough gold! ${building.name} in ${city.name} was sold to cover upkeep.`);
       } else if (e.type === 'spaceshipPart' && e.civ === human) {
         const city = Logic.cityById(this.state, e.cityId);
         const part = this.rules.units[e.part];