提交缺失语言文件

lib/enum/SignalLevel.dart

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+// 信号强度等级枚举
+enum SignalLevel {
+  none(0, '无信号'),
+  poor(1, '信号弱'),
+  fair(2, '信号中'),
+  good(3, '信号良'),
+  excellent(4, '信号强');
+
+  final int level;
+  final String description;
+  const SignalLevel(this.level, this.description);
+}