feat(lite): add opt-in tun ipv6 mode

lite/main.py

@@ -1312,6 +1312,15 @@ def _set_tun_dns_servers(value):
     data["tun_dns"] = list(parsed)
     _settings_save(data)
 
+def _tun_ipv6_enabled():
+    """TUN IPv6 默认关闭，避免未验证的 IPv6 路径接管系统流量。"""
+    return bool(_settings_load().get("tun_ipv6_enabled", False))
+
+def _set_tun_ipv6_enabled(value):
+    data = _settings_load()
+    data["tun_ipv6_enabled"] = bool(value)
+    _settings_save(data)
+
 def _use_system_pac():
     """只决定 Windows 系统代理是否使用 PAC；旧设置按原行为读取。"""
     data = _settings_load()
@@ -2632,6 +2641,7 @@ def _settings_services():
         get_port=lambda: _TLS_LOCAL_PORT,
         get_system_pac=_use_system_pac,
         get_dns=_tun_dns_servers,
+        get_ipv6_enabled=_tun_ipv6_enabled,
         get_update_via_proxy=_update_via_proxy,
         get_skip_update_check=_skip_update_check,
         get_node_display_mode=_node_display_mode,
@@ -2640,6 +2650,7 @@ def _settings_services():
         set_port=_set_local_port,
         set_system_pac=_set_use_system_pac,
         set_dns=_set_tun_dns_servers,
+        set_ipv6_enabled=_set_tun_ipv6_enabled,
         set_update_via_proxy=_set_update_via_proxy,
         set_skip_update_check=_set_skip_update_check,
         set_node_display_mode=_set_node_display_mode,
@@ -2722,6 +2733,7 @@ def _start_tun_backend(backend, payload):
         bypass_lan=bypass_lan,
         route_rules=rules,
         dns_servers=payload["dns_servers"],
+        ipv6_enabled=bool(payload.get("ipv6_enabled", False)),
         direct_target_resolver=direct_target,
         route_rule_resolver=user_rule,
         route_node_resolver=route_node,
@@ -2748,6 +2760,7 @@ def _tun_start_payload(use_pac, bypass_lan):
         "route_rules": _route_rules(),
         "route_nodes": route_nodes,
         "dns_servers": _tun_dns_servers(),
+        "ipv6_enabled": _tun_ipv6_enabled(),
         "bypass_lan": bool(bypass_lan),
         "smart": bool(use_pac),
     }