feat: add BleStatus enum and BleCallbacks interface

android/app/src/main/java/com/eddy/atomrelay/BleStatus.kt

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package com.eddy.atomrelay
+
+enum class BleStatus {
+    Scanning,
+    Connecting,
+    Connected,
+    Disconnected,
+    NoKey,
+    WrongDevice,
+    ServiceNotFound,
+    ServiceError,
+    CommError,
+    DeviceNotFound,
+    BluetoothDisabled,
+    PermissionsDenied
+}
+
+interface BleCallbacks {
+    fun onStatusChanged(status: BleStatus)
+}