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backend/services/notification_manager.py

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+"""
+Manages persistent per-user WebSocket connections for the notification channel.
+The DB is the source of truth — this layer just delivers live pushes to connected clients.
+"""
+import logging
+
+from fastapi import WebSocket
+
+logger = logging.getLogger("app")
+
+# user_id (str) -> active WebSocket; replaced on reconnect
+connections: dict[str, WebSocket] = {}
+
+
+def register(user_id: str, ws: WebSocket) -> None:
+  connections[user_id] = ws
+
+
+def unregister(user_id: str) -> None:
+  connections.pop(user_id, None)
+
+
+async def send_notification(user_id: str, notification: dict) -> None:
+  """Push a single notification to the user if they're connected. No-op otherwise."""
+  ws = connections.get(user_id)
+  if ws:
+    try:
+      await ws.send_json({"type": "push", "notification": notification})
+    except Exception as e:
+      # Stale connection — the disconnect handler will clean it up
+      logger.debug(f"WebSocket send failed (stale connection): {e}")
+
+
+async def send_delete(user_id: str, notification_id: str) -> None:
+  """Tell the client to remove a notification from its local list."""
+  ws = connections.get(user_id)
+  if ws:
+    try:
+      await ws.send_json({"type": "delete", "notification_id": notification_id})
+    except Exception as e:
+      logger.debug(f"WebSocket send failed (stale connection): {e}")