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/products/intercept.go

@@ -60,6 +60,11 @@ func (p *Products) interceptXMLRPC(x *proxy.Exchange) error {
 	case "test.avatarInfoForLogin2":
 		x.ModifyResponse = func(resp *http.Response, body []byte) ([]byte, error) {
 			p.keys.learn(body)
+			if m := userIDPattern.FindSubmatch(body); m != nil {
+				p.mu.Lock()
+				p.user = string(m[1])
+				p.mu.Unlock()
+			}
 			if m := userIDPattern.FindSubmatch(body); m != nil && p.Observer != nil {
 				if id, err := strconv.ParseInt(string(m[1]), 10, 64); err == nil {
 					p.Observer.Session(id)