feat(frontend): polish connection tree and terminal groups

Add explorer-style tree search in the connections view with
match-path expansion, clearer count highlighting, and a refined
sidebar header layout.

Improve terminal tab grouping by keeping new sessions appended
within their server group, highlighting the active group, and
deduplicating broadcast actions to send commands once per server.

packages/frontend/src/locales/zh-CN.json

@@ -1319,10 +1319,10 @@
     "copied": "已复制到剪贴板",
     "copyFailed": "复制失败",
     "actions": {
-      "sendToAllSessions": "发送到全部会话"
+      "sendToAllSessions": "发送到全部服务器"
     },
     "notifications": {
-      "sentToAllSessions": "指令已发送到 {count} 个会话。",
+      "sentToAllSessions": "指令已发送到 {count} 台服务器。",
       "noActiveSshSessions": "没有活动的 SSH 会话可发送指令。"
     }
   },
@@ -1360,10 +1360,10 @@
       "clickToEditTag": "点击编辑标签名称"
     },
     "actions": {
-      "sendToAllSessions": "发送到全部会话"
+      "sendToAllSessions": "发送到全部服务器"
     },
     "notifications": {
-      "sentToAllSessions": "指令已发送到 {count} 个会话。",
+      "sentToAllSessions": "指令已发送到 {count} 台服务器。",
       "noActiveSshSessions": "没有活动的 SSH 会话可发送指令。"
     }
   },