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_helpers.go

@@ -65,7 +65,7 @@ func doAckSimpleFail(s *Session, ackHandle uint32, data []byte) {
 func updateRights(s *Session) {
 	rightsInt := uint32(2)
 	_ = s.server.db.QueryRow("SELECT rights FROM users u INNER JOIN characters c ON u.id = c.user_id WHERE c.id = $1", s.charID).Scan(&rightsInt)
-	s.courses, rightsInt = mhfcourse.GetCourseStruct(rightsInt)
+	s.courses, rightsInt = mhfcourse.GetCourseStruct(rightsInt, s.server.erupeConfig.DefaultCourses)
 	update := &mhfpacket.MsgSysUpdateRight{
 		ClientRespAckHandle: 0,
 		Bitfield:            rightsInt,