use inventory hostname as default server name

defaults/main.yml

@@ -1,6 +1,8 @@
 gitea_http_addr: 127.0.0.1
 gitea_http_port: 3000
 
+gitea_server_name: "{{ inventory_hostname }}"
+
 gitea_download_version: 1.5.1
 gitea_download_url: https://dl.gitea.io/gitea/{{gitea_download_version}}/gitea-{{gitea_download_version}}-linux-amd64
 #gitea_download_url: https://github.com/go-gitea/gitea/releases/download/v{{gitea_download_version}}/gitea-{{gitea_download_version}}-linux-amd64