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/sys_session.go

@@ -81,9 +81,9 @@ func NewSession(server *Server, conn net.Conn) *Session {
 		logger:         server.logger.Named(conn.RemoteAddr().String()),
 		server:         server,
 		rawConn:        conn,
-		cryptConn:      network.NewCryptConn(conn),
+		cryptConn:      network.NewCryptConn(conn, server.erupeConfig.RealClientMode),
 		sendPackets:    make(chan packet, 20),
-		clientContext:  &clientctx.ClientContext{},
+		clientContext:  &clientctx.ClientContext{RealClientMode: server.erupeConfig.RealClientMode},
 		lastPacket:     time.Now(),
 		objectID:       server.getObjectId(),
 		sessionStart:   TimeAdjusted().Unix(),