fix: editable alias in server dialog + Ctrl+Z undo for all input fields

- Alias field no longer disabled when editing server profile
- Duplicate alias check on rename, session pool migration
- Enable undo (Ctrl+Z) on all CTkEntry widgets across the project

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/i18n.py

@@ -90,6 +90,7 @@ _EN = {
     "show": "Show",
     "hide": "Hide",
     "alias_required": "Alias is required",
+    "alias_exists": "Alias '{alias}' already exists",
     "ip_required": "IP is required",
     "port_must_be_number": "Port must be a number",
     "error_prefix": "Error: {msg}",
@@ -355,6 +356,7 @@ _RU = {
     "show": "Показать",
     "hide": "Скрыть",
     "alias_required": "Алиас обязателен",
+    "alias_exists": "Алиас '{alias}' уже существует",
     "ip_required": "IP обязателен",
     "port_must_be_number": "Порт должен быть числом",
     "error_prefix": "Ошибка: {msg}",
@@ -620,6 +622,7 @@ _ZH = {
     "show": "显示",
     "hide": "隐藏",
     "alias_required": "别名不能为空",
+    "alias_exists": "别名 '{alias}' 已存在",
     "ip_required": "IP不能为空",
     "port_must_be_number": "端口必须是数字",
     "error_prefix": "错误：{msg}",

core/server_store.py

@@ -357,7 +357,14 @@ class ServerStore:
         servers = self._data.get("servers", [])
         for i, s in enumerate(servers):
             if s["alias"] == alias:
+                new_alias = updated.get("alias", alias)
                 servers[i] = updated
+                # If alias changed, migrate status
+                if new_alias != alias:
+                    with self._statuses_lock:
+                        old_status = self._statuses.pop(alias, None)
+                        if old_status:
+                            self._statuses[new_alias] = old_status
                 self._save()
                 self._notify()
                 return

core/session_pool.py

@@ -214,6 +214,17 @@ class SessionPool:
         """Clean up sessions when a server is deleted."""
         self.disconnect_session(alias)
 
+    def rename_server(self, old_alias: str, new_alias: str):
+        """Rename a server's session references (after alias change)."""
+        with self._lock:
+            if old_alias in self._sessions:
+                session_data = self._sessions.pop(old_alias)
+                session_data.alias = new_alias
+                self._sessions[new_alias] = session_data
+            if old_alias in self._last_used_order:
+                ts = self._last_used_order.pop(old_alias)
+                self._last_used_order[new_alias] = ts
+
     def get_active_sessions(self) -> list:
         """Get list of aliases for active sessions."""
         with self._lock: