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/integration_test.go

@@ -621,16 +621,13 @@ func IntegrationTest_ClientVersionCompatibility(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			originalVersion := _config.ErupeConfig.RealClientMode
-			defer func() { _config.ErupeConfig.RealClientMode = originalVersion }()
-
-			_config.ErupeConfig.RealClientMode = tt.clientVersion
-
 			mock := &MockCryptConn{sentPackets: make([][]byte, 0)}
 			s := &Session{
 				sendPackets: make(chan packet, 100),
-					server: &Server{
-					erupeConfig: _config.ErupeConfig,
+				server: &Server{
+					erupeConfig: &_config.Config{
+						RealClientMode: tt.clientVersion,
+					},
 				},
 			}
 			s.cryptConn = mock