fix: add missing os_listener toggle to notification CSS editor

The os_listener field existed in the backend model but was never
exposed in the UI. It defaulted to false, so OS notifications were
captured to history but never fired the visual effect. Now shows
a toggle at the top of the notification section, defaults to ON
for new sources.

server/src/wled_controller/static/locales/zh.json

@@ -1047,6 +1047,8 @@
     "color_strip.type.notification": "通知",
     "color_strip.type.notification.desc": "通过Webhook触发的一次性效果",
     "color_strip.type.notification.hint": "通过 Webhook 触发时显示一次性视觉效果（闪烁、脉冲、扫描）。设计为组合源中的叠加层。",
+    "color_strip.notification.os_listener": "监听系统通知：",
+    "color_strip.notification.os_listener.hint": "启用后，当桌面通知出现时（Windows toast / Linux D-Bus），此源会自动触发。需要应用具有通知访问权限。",
     "color_strip.notification.effect": "效果：",
     "color_strip.notification.effect.hint": "通知触发时的视觉效果。闪烁线性衰减，脉冲平滑钟形曲线，扫描从左到右填充后衰减。",
     "color_strip.notification.effect.flash": "闪烁",