refactor(config): eliminate ErupeConfig global variable

Replace the mutable global `_config.ErupeConfig` with dependency
injection across 79 files. Config is now threaded through existing
paths: `ClientContext.RealClientMode` for packet encoding, `s.server.
erupeConfig` for channel handlers, and explicit parameters for utility
functions. This removes hidden coupling, enables test parallelism
without global save/restore, and prevents low-level packages from
reaching up to the config layer.

Key changes:
- Enrich ClientContext with RealClientMode for packet files
- Add mode parameter to CryptConn, mhfitem, mhfcourse functions
- Convert handlers_commands init() to lazy sync.Once initialization
- Delete global var, init(), and helper functions from config.go
- Update all tests to pass config explicitly

network/mhfpacket/msg_sys_terminal_log.go

@@ -49,7 +49,7 @@ func (m *MsgSysTerminalLog) Parse(bf *byteframe.ByteFrame, ctx *clientctx.Client
 		e.Unk1 = bf.ReadInt32()
 		e.Unk2 = bf.ReadInt32()
 		e.Unk3 = bf.ReadInt32()
-		if _config.ErupeConfig.RealClientMode >= _config.G1 {
+		if ctx.RealClientMode >= _config.G1 {
 			for j := 0; j < 4; j++ {
 				e.Unk4 = append(e.Unk4, bf.ReadInt32())
 			}