feat: 实现日志级别功能并修复日志输出问题

- 实现 logging.level 配置项支持（DEBUG/INFO/WARN/ERROR）
- 修复日志文件中 ANSI 颜色代码显示问题
- 修复 install.sh 中 show_info() 函数颜色显示
- 日志输出现在会根据配置的级别进行过滤

install.sh

@@ -343,53 +343,51 @@ test_backup() {
 ###############################################################################
 
 show_info() {
-    cat << EOF
-
-${GREEN}╔═══════════════════════════════════════════════════════════════╗
-║                 Docker Backup 安装完成！                      ║
-╚═══════════════════════════════════════════════════════════════╝${NC}
-
-${BLUE}安装信息:${NC}
-  - 备份脚本: ${BIN_DIR}/docker-backup
-  - 清理脚本: ${BIN_DIR}/docker-backup-cleanup
-  - 配置文件: ${CONFIG_DIR}/config.yml
-  - 服务名称: ${SERVICE_NAME}
-
-${BLUE}常用命令:${NC}
-  # 查看定时任务状态
-  systemctl status ${SERVICE_NAME}.timer
-
-  # 查看定时计划
-  systemctl list-timers ${SERVICE_NAME}.timer
-
-  # 手动执行备份
-  docker-backup
-
-  # 列出所有备份
-  docker-backup-cleanup --list
-
-  # 清理旧备份
-  docker-backup-cleanup --auto
-
-  # 停止定时任务
-  systemctl stop ${SERVICE_NAME}.timer
-
-  # 禁用定时任务
-  systemctl disable ${SERVICE_NAME}.timer
-
-${YELLOW}重要提示:${NC}
-  1. 请编辑配置文件以适应您的环境:
-     vi ${CONFIG_DIR}/config.yml
-
-  2. 修改配置后无需重启服务，下次执行时自动生效
-
-  3. 查看下次执行时间:
-     systemctl list-timers | grep ${SERVICE_NAME}
-
-  4. 查看备份日志:
-     journalctl -u ${SERVICE_NAME}.service -f
-
-EOF
+    echo ""
+    echo -e "${GREEN}╔═══════════════════════════════════════════════════════════════╗${NC}"
+    echo -e "${GREEN}║                 Docker Backup 安装完成！                      ║${NC}"
+    echo -e "${GREEN}╚═══════════════════════════════════════════════════════════════╝${NC}"
+    echo ""
+    echo -e "${BLUE}安装信息:${NC}"
+    echo "  - 备份脚本: ${BIN_DIR}/docker-backup"
+    echo "  - 清理脚本: ${BIN_DIR}/docker-backup-cleanup"
+    echo "  - 配置文件: ${CONFIG_DIR}/config.yml"
+    echo "  - 服务名称: ${SERVICE_NAME}"
+    echo ""
+    echo -e "${BLUE}常用命令:${NC}"
+    echo "  # 查看定时任务状态"
+    echo "  systemctl status ${SERVICE_NAME}.timer"
+    echo ""
+    echo "  # 查看定时计划"
+    echo "  systemctl list-timers ${SERVICE_NAME}.timer"
+    echo ""
+    echo "  # 手动执行备份"
+    echo "  docker-backup"
+    echo ""
+    echo "  # 列出所有备份"
+    echo "  docker-backup-cleanup --list"
+    echo ""
+    echo "  # 清理旧备份"
+    echo "  docker-backup-cleanup --auto"
+    echo ""
+    echo "  # 停止定时任务"
+    echo "  systemctl stop ${SERVICE_NAME}.timer"
+    echo ""
+    echo "  # 禁用定时任务"
+    echo "  systemctl disable ${SERVICE_NAME}.timer"
+    echo ""
+    echo -e "${YELLOW}重要提示:${NC}"
+    echo "  1. 请编辑配置文件以适应您的环境:"
+    echo "     vi ${CONFIG_DIR}/config.yml"
+    echo ""
+    echo "  2. 修改配置后无需重启服务，下次执行时自动生效"
+    echo ""
+    echo "  3. 查看下次执行时间:"
+    echo "     systemctl list-timers | grep ${SERVICE_NAME}"
+    echo ""
+    echo "  4. 查看备份日志:"
+    echo "     journalctl -u ${SERVICE_NAME}.service -f"
+    echo ""
 }
 
 ###############################################################################
@@ -509,18 +507,16 @@ main() {
     done
 
     # 显示欢迎信息
-    cat << EOF
-${GREEN}╔═══════════════════════════════════════════════════════════════╗
-║            欢迎使用 Docker Backup 安装程序                     ║
-╚═══════════════════════════════════════════════════════════════╝${NC}
-
-安装配置:
-  - 服务名称: ${SERVICE_NAME}
-  - 定时计划: ${SCHEDULE}
-  - 配置目录: ${CONFIG_DIR}
-  - 脚本目录: ${BIN_DIR}
-
-EOF
+    echo -e "${GREEN}╔═══════════════════════════════════════════════════════════════╗${NC}"
+    echo -e "${GREEN}║            欢迎使用 Docker Backup 安装程序                     ║${NC}"
+    echo -e "${GREEN}╚═══════════════════════════════════════════════════════════════╝${NC}"
+    echo ""
+    echo "安装配置:"
+    echo "  - 服务名称: ${SERVICE_NAME}"
+    echo "  - 定时计划: ${SCHEDULE}"
+    echo "  - 配置目录: ${CONFIG_DIR}"
+    echo "  - 脚本目录: ${BIN_DIR}"
+    echo ""
 
     # 检查 root 权限
     check_root