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_packets_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"erupe-ce/common/byteframe"
+	_config "erupe-ce/config"
 	"erupe-ce/network"
 	"erupe-ce/network/clientctx"
 )
@@ -34,7 +35,7 @@ func TestMsgSysCastBinaryParse(t *testing.T) {
 			_, _ = bf.Seek(0, io.SeekStart)
 
 			pkt := &MsgSysCastBinary{}
-			err := pkt.Parse(bf, &clientctx.ClientContext{})
+			err := pkt.Parse(bf, &clientctx.ClientContext{RealClientMode: _config.ZZ})
 			if err != nil {
 				t.Fatalf("Parse() error = %v", err)
 			}