docs: add doc.go files and godoc comments to all packages

Add package-level documentation (doc.go) to all 22 first-party
packages and godoc comments to ~150 previously undocumented
exported symbols across common/, network/, and server/.

network/binpacket/doc.go

@@ -0,0 +1,4 @@
+// Package binpacket defines higher-level binary message types that are carried
+// inside MSG_SYS_CAST_BINARY / MSG_SYS_CASTED_BINARY packets. These include
+// chat messages, mail notifications, and targeted player broadcasts.
+package binpacket

network/binpacket/msg_bin_mail_notify.go

@@ -6,20 +6,24 @@ import (
 	"erupe-ce/network"
 )
 
+// MsgBinMailNotify is a binpacket broadcast to notify a player of new mail.
 type MsgBinMailNotify struct {
 	SenderName string
 }
 
+// Parse parses the packet from binary.
 func (m MsgBinMailNotify) Parse(bf *byteframe.ByteFrame) error {
 	panic("implement me")
 }
 
+// Build builds a binary packet from the current data.
 func (m MsgBinMailNotify) Build(bf *byteframe.ByteFrame) error {
 	bf.WriteUint8(0x01) // Unk
 	bf.WriteBytes(stringsupport.PaddedString(m.SenderName, 21, true))
 	return nil
 }
 
+// Opcode returns the ID associated with this packet type.
 func (m MsgBinMailNotify) Opcode() network.PacketID {
 	return network.MSG_SYS_CASTED_BINARY
 }