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_campaign.go

@@ -71,7 +71,7 @@ func handleMsgMhfEnumerateCampaign(s *Session, p mhfpacket.MHFPacket) {
 		bf.WriteInt16(event.MaxHR)
 		bf.WriteInt16(event.MinSR)
 		bf.WriteInt16(event.MaxSR)
-		if _config.ErupeConfig.RealClientMode >= _config.G3 {
+		if s.server.erupeConfig.RealClientMode >= _config.G3 {
 			bf.WriteInt16(event.MinGR)
 			bf.WriteInt16(event.MaxGR)
 		}