Refresh the inventory on the user's queue, which the client joins by connecting

The client never subscribes to its user queue; the proxy now follows every IMQ connection and the signed-in
account (from the login answer), and delivers the refresh event on /user/<id>. Checked live: removing a product
from the library on the hub reloads the client's inventory.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/proxy/connect.go

@@ -74,6 +74,7 @@ func (s *Server) serveConnect(w http.ResponseWriter, r *http.Request) {
 		c := &IMQConn{ID: id, w: toClient}
 		down.watcher, down.conn = w, c
 		up.watcher, up.conn = w, c
+		w.Opened(c)
 		defer w.Closed(c)
 	}
 	// IMQ is a session: when either side closes, it's over, so both connections close.
@@ -111,6 +112,8 @@ type IMQFilter interface {
 // messages the gateway delivers (which it can change), and it can deliver messages of its own.
 type IMQWatcher interface {
 	IMQFilter
+	// Opened: the client opened an IMQ connection (its user queue comes with it, without a subscription).
+	Opened(c *IMQConn)
 	// Subscribed and Unsubscribed see the client's subscriptions on a connection.
 	Subscribed(c *IMQConn, queues []string)
 	Unsubscribed(c *IMQConn, queues []string)