refactor: use bin instead of build directory

Makefile

@@ -14,7 +14,7 @@ help: ## Display this help screen
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'
 
 build:
-	go build -ldflags "-s -w" -o build/app .
+	go build -ldflags "-s -w" -o bin/app .
 
 run:
 	make build-backoffice-gateway