feat(remote): 修复键盘输入映射并重构连接流程

- Android端注入按键时显式设置SOURCE_KEYBOARD，修复IME丢弃事件导致输入框无法输入文字的问题
- Flutter端新增Flutter逻辑键到Android keyCode的转换映射，避免功能键误触发
- 重构RemoteController，分离信令连接与远程控制逻辑，支持设备列表选择与配对码兑换
- AuthRepository接口新增getBindings、getOnlineDevices、redeemPairingCode方法
- DioAuthRepository实现401自动刷新token重试机制
- ConnectionSessionState扩展设备列表、在线状态、配对码等状态字段

webrtc_controller_flutter/lib/l10n/app_localizations_en.dart

@@ -49,12 +49,6 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get connectDevice => 'Connect Device';
 
-  @override
-  String get serverUrl => 'Signal Server URL:';
-
-  @override
-  String get serverUrlPlaceholder => 'wss://www.ttstd.com/signal';
-
   @override
   String get deviceId => 'Device ID (assigned by server):';
 
@@ -82,8 +76,7 @@ class AppLocalizationsEn extends AppLocalizations {
   String get usernamePasswordRequired => 'Please enter username and password';
 
   @override
-  String get serverAndTargetRequired =>
-      'Please enter server URL and target device ID';
+  String get targetRequired => 'Please enter target device ID';
 
   @override
   String get authTitle => 'Connection Auth';
@@ -239,4 +232,42 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get streamModeSelfCodecDesc =>
       'Self-codec hardware decoding is not supported on this platform.';
+
+  @override
+  String get boundDevices => 'Bound Devices';
+
+  @override
+  String get online => 'Online';
+
+  @override
+  String get offline => 'Offline';
+
+  @override
+  String get noBoundDevices => 'No bound devices yet';
+
+  @override
+  String get refreshDevices => 'Refresh';
+
+  @override
+  String get redeemPairingCode => 'Bind with Pairing Code';
+
+  @override
+  String get pairingCodeHint =>
+      'Enter the pairing code shown on the controlled device';
+
+  @override
+  String bindingFailed(Object error) {
+    return 'Binding failed: $error';
+  }
+
+  @override
+  String deviceOfflineCannotConnect(Object name) {
+    return 'Device \"$name\" is currently offline and cannot be connected';
+  }
+
+  @override
+  String get pleaseSelectDevice => 'Please select a bound device first';
+
+  @override
+  String get bindSuccess => 'Bound successfully';
 }