fix: etcp_router_consumer_ack — use router_ack_do_send instead of schedule

router_schedule_ack skips when rx_seq==last_sent_ack_seq (no-op),
so the first consumer_ack call after setting consumer_ack=1 was
silently ignored. Client never got ACK → send_q stuck at 256.

router_ack_do_send always sends the ACK unconditionally.

src/etcp_router.c

@@ -557,7 +557,7 @@ void etcp_router_consumer_ack(struct UTUN_INSTANCE* inst, uint64_t remote_node_i
     struct ETCP_ROUTER_CONN* rconn = etcp_router_conn_get(inst, remote_node_id, svc_id);
     if (!rconn) return;
     rconn->consumer_ack = 1;
-    router_schedule_ack(rconn);
+    router_ack_do_send(rconn);
 }
 
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