fix(pairing): broadcast pairing events for SQLite stores, not just PG

SetOnRequest was only wired for PGPairingStore via concrete type assertion.
Use interface-based assertion so SQLitePairingStore also gets the callback.
This fixes desktop app not receiving real-time pairing request notifications.

cmd/gateway.go

@@ -511,7 +511,11 @@ func runGateway() {
 
 	// Wire pairing event broadcasts to all WS clients.
 	pairingMethods.SetBroadcaster(server.BroadcastEvent)
-	if ps, ok := pgStores.Pairing.(*pg.PGPairingStore); ok {
+	// Wire pairing request callback — works for both PG and SQLite stores.
+	type pairingRequestNotifier interface {
+		SetOnRequest(func(code, senderID, channel, chatID string))
+	}
+	if ps, ok := pgStores.Pairing.(pairingRequestNotifier); ok {
 		ps.SetOnRequest(func(code, senderID, channel, chatID string) {
 			server.BroadcastEvent(*protocol.NewEvent(protocol.EventDevicePairReq, map[string]any{
 				"code": code, "sender_id": senderID, "channel": channel, "chat_id": chatID,