Unified BtDevice Object (#940)

https://github.com/user-attachments/assets/74687e5c-49c4-4dfa-9302-0e9e32452c14



<!-- This is an auto-generated comment: release notes by OSS
Entelligence.AI -->
### Summary by Entelligence.AI

- Refactor: Unified the Bluetooth device handling across the application
by introducing a new `BtDevice` class and `BtDeviceInfo` class. This
change improves the consistency of device information retrieval and
storage.
- New Feature: Added methods for creating `BtDevice` instances from
different sources, providing more flexibility in device management.
- Refactor: Updated import paths for better organization of the
codebase.
- Refactor: Adjusted button actions related to device disconnection and
unpairing for improved user experience.
- Refactor: Streamlined the usage of the `BtDevice` object consistently
throughout the code, enhancing code maintainability.
- Bug Fix: Fixed potential issues with fetching device info by adding
checks in `initState`.
- Chore: Updated references to properties within `BtDevice` in various
parts of the code for consistency.
<!-- end of auto-generated comment: release notes by OSS Entelligence.AI
-->

app/lib/backend/preferences.dart

@@ -1,9 +1,9 @@
 import 'dart:convert';
 
 import 'package:collection/collection.dart';
-import 'package:friend_private/backend/schema/bt_device.dart';
 import 'package:friend_private/backend/schema/memory.dart';
 import 'package:friend_private/backend/schema/message.dart';
+import 'package:friend_private/backend/schema/bt_device/bt_device.dart';
 import 'package:friend_private/backend/schema/person.dart';
 import 'package:friend_private/backend/schema/plugin.dart';
 import 'package:friend_private/backend/schema/transcript_segment.dart';
@@ -27,18 +27,18 @@ class SharedPreferencesUtil {
 
   String get uid => getString('uid') ?? '';
 
-  set btDeviceStruct(BTDeviceStruct value) {
-    saveString('btDeviceStruct', jsonEncode(value.toJson()));
+  set btDevice(BtDevice value) {
+    saveString('btDevice', jsonEncode(value.toJson()));
   }
 
-  Future<void> btDeviceStructSet(BTDeviceStruct value) async {
-    await saveString('btDeviceStruct', jsonEncode(value.toJson()));
+  Future<void> btDeviceSet(BtDevice value) async {
+    await saveString('btDevice', jsonEncode(value.toJson()));
   }
 
-  BTDeviceStruct get btDeviceStruct {
-    final String device = getString('btDeviceStruct') ?? '';
-    if (device.isEmpty) return BTDeviceStruct(id: '', name: '');
-    return BTDeviceStruct.fromJson(jsonDecode(device));
+  BtDevice get btDevice {
+    final String device = getString('btDevice') ?? '';
+    if (device.isEmpty) return BtDevice(id: '', name: '', type: DeviceType.friend, rssi: 0);
+    return BtDevice.fromJson(jsonDecode(device));
   }
 
   set deviceName(String value) => saveString('deviceName', value);