refactor(channelserver): add numeric column helpers and extract protocol constants

Add readCharacterInt/adjustCharacterInt helpers for single-column
integer operations on the characters table. Eliminates fmt.Sprintf
SQL construction in handlers_misc.go and replaces inline queries
across cafe, kouryou, and mercenary handlers.

Second round of protocol constant extraction: adds constants_time.go
(secsPerDay, secsPerWeek), constants_raviente.go (register IDs,
semaphore constants), and named constants across 14 handler files
replacing raw hex/numeric literals. Updates anti-patterns doc to
mark #4 (magic numbers) as substantially fixed.

server/channelserver/handlers_reward.go

@@ -12,7 +12,8 @@ func handleMsgMhfGetAdditionalBeatReward(s *Session, p mhfpacket.MHFPacket) {
 	// Actual response in packet captures are all just giant batches of null bytes
 	// I'm assuming this is because it used to be tied to an actual event and
 	// they never bothered killing off the packet when they made it static
-	doAckBufSucceed(s, pkt.AckHandle, make([]byte, 0x104))
+	const beatRewardResponseSize = 0x104
+	doAckBufSucceed(s, pkt.AckHandle, make([]byte, beatRewardResponseSize))
 }
 
 func handleMsgMhfGetUdRankingRewardList(s *Session, p mhfpacket.MHFPacket) {