feat(client): 节点列表防误触 — 已连接时切换节点先弹确认

未连接(off)点节点直接选→跳连接页(无破坏性,不弹框);已连接/连接中点其他
节点会断开重连,先弹确认框(标题含目标节点名),取消则维持当前连接。新增
nodeSwitchTitle/Body/Confirm 三条文案 + node_connect_confirm_test 覆盖 off/on 两路。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/l10n/strings_en.dart

@@ -64,6 +64,12 @@ class StringsEn extends AppText {
   @override
   String get smartSelect => 'Smart select';
   @override
+  String nodeSwitchTitle(String name) => 'Switch to $name?';
+  @override
+  String get nodeSwitchBody => 'This disconnects the current link and reconnects to this node.';
+  @override
+  String get nodeSwitchConfirm => 'Switch';
+  @override
   String get smartSub => 'Picks the best node for your network';
   @override
   String get recommended => 'Recommended';