Keep the gateway connection alive and resume hosted queues after reconnecting

The client doesn't ping while it's sending, so when the proxy answers its frames itself (everything it
sends in a hosted room), IMVU's gateway saw an idle connection and closed it after about a minute. A
ping now goes to the gateway in place of each answered frame. And after a reconnect, hosted rooms'
queues are taken out of C2gOpenFloodgates and answered here (the gateway never answered them, so the
client gave up and closed the room).

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

internal/imq/frame_test.go

@@ -97,3 +97,17 @@ func TestSubscriptionOps(t *testing.T) {
 		t.Fatalf("all %v", all)
 	}
 }
+
+func TestFloodgates(t *testing.T) {
+	state := func(q string, seq, op uint64) []byte {
+		return appendVarintField(appendVarintField(appendBytesField(nil, 1, []byte(q)), 2, seq), 3, op)
+	}
+	data := appendBytesField(appendBytesField(nil, 1, state("/user/1", 38, 19)), 1, state("/chat/2100000001", 29, 20))
+	states, err := ParseFloodgates(data)
+	if err != nil || len(states) != 2 || states[1].Queue != "/chat/2100000001" || states[1].OpID != 20 {
+		t.Fatalf("%+v %v", states, err)
+	}
+	if string(MarshalFloodgates(states)) != string(data) || string(MarshalFloodgates(states[:1])) != string(appendBytesField(nil, 1, state("/user/1", 38, 19))) {
+		t.Fatal("re-encoded differently")
+	}
+}