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_cafe.go

@@ -102,7 +102,7 @@ func handleMsgMhfGetCafeDuration(s *Session, p mhfpacket.MHFPacket) {
 		cafeTime = uint32(TimeAdjusted().Unix()) - uint32(s.sessionStart) + cafeTime
 	}
 	bf.WriteUint32(cafeTime)
-	if _config.ErupeConfig.RealClientMode >= _config.ZZ {
+	if s.server.erupeConfig.RealClientMode >= _config.ZZ {
 		bf.WriteUint16(0)
 		ps.Uint16(bf, fmt.Sprintf(s.server.i18n.cafe.reset, int(cafeReset.Month()), cafeReset.Day()), true)
 	}