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

server/channelserver/handlers_house_test.go

@@ -1,6 +1,7 @@
 package channelserver
 
 import (
+	_config "erupe-ce/config"
 	"erupe-ce/common/mhfitem"
 	"erupe-ce/common/token"
 	"testing"
@@ -92,7 +93,7 @@ func TestWarehouseEquipmentSerialization(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			// Serialize
-			serialized := mhfitem.SerializeWarehouseEquipment(tt.equipment)
+			serialized := mhfitem.SerializeWarehouseEquipment(tt.equipment, _config.ZZ)
 
 			// Basic validation
 			if serialized == nil {