fix(channelserver): add max-size guards to binary blob save handlers

A malicious or buggy client could send arbitrarily large payloads
that get written directly to PostgreSQL, wasting disk and memory.
Each save handler now rejects payloads exceeding a generous upper
bound derived from the known data format sizes.

Covers all remaining items from #158: partner, hunternavi,
savemercenary, scenariodata, platedata, platebox, platemyset,
rengokudata, mezfes, savefavoritequest, house_furniture, mission.

Closes #158

server/channelserver/handlers_rengoku.go

@@ -16,8 +16,8 @@ func handleMsgMhfSaveRengokuData(s *Session, p mhfpacket.MHFPacket) {
 	// saved every floor on road, holds values such as floors progressed, points etc.
 	// can be safely handled by the client
 	pkt := p.(*mhfpacket.MsgMhfSaveRengokuData)
-	if len(pkt.RawDataPayload) < 91 {
-		s.logger.Warn("Rengoku payload too short", zap.Int("len", len(pkt.RawDataPayload)))
+	if len(pkt.RawDataPayload) < 91 || len(pkt.RawDataPayload) > 4096 {
+		s.logger.Warn("Rengoku payload size out of range", zap.Int("len", len(pkt.RawDataPayload)))
 		doAckSimpleSucceed(s, pkt.AckHandle, make([]byte, 4))
 		return
 	}