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_commands.go

@@ -44,6 +44,8 @@ func sendDisabledCommandMessage(s *Session, cmd _config.Command) {
 	sendServerChatMessage(s, fmt.Sprintf(s.server.i18n.commands.disabled, cmd.Name))
 }
 
+const chatFlagServer = 0x80 // marks a message as server-originated
+
 func sendServerChatMessage(s *Session, message string) {
 	// Make the inside of the casted binary
 	bf := byteframe.NewByteFrame()
@@ -51,7 +53,7 @@ func sendServerChatMessage(s *Session, message string) {
 	msgBinChat := &binpacket.MsgBinChat{
 		Unk0:       0,
 		Type:       5,
-		Flags:      0x80,
+		Flags:      chatFlagServer,
 		Message:    message,
 		SenderName: "Erupe",
 	}