Add OS notification listener for Windows toast capture

Polls Windows notifications via winsdk UserNotificationListener API
and fires matching notification CSS streams with os_listener=True.
Includes history API endpoint for tracking captured notifications.

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

server/src/wled_controller/api/routes/color_strip_sources.py

@@ -570,6 +570,19 @@ async def notify_source(
     }
 
 
+@router.get("/api/v1/color-strip-sources/os-notifications/history", tags=["Color Strip Sources"])
+async def os_notification_history(_auth: AuthRequired):
+    """Return recent OS notification capture history (newest first)."""
+    from wled_controller.core.processing.os_notification_listener import get_os_notification_listener
+    listener = get_os_notification_listener()
+    if listener is None:
+        return {"available": False, "history": []}
+    return {
+        "available": listener._available,
+        "history": listener.recent_history,
+    }
+
+
 @router.websocket("/api/v1/color-strip-sources/{source_id}/ws")
 async def css_api_input_ws(
     websocket: WebSocket,