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/entranceserver/make_resp.go

@@ -63,8 +63,8 @@ func encodeServerInfo(config *_config.Config, s *Server, local bool) []byte {
 
 		for channelIdx, ci := range si.Channels {
 			sid := (serverIdx<<8 | 4096) + (channelIdx | 16)
-			if _config.ErupeConfig.DebugOptions.ProxyPort != 0 {
-				bf.WriteUint16(_config.ErupeConfig.DebugOptions.ProxyPort)
+			if config.DebugOptions.ProxyPort != 0 {
+				bf.WriteUint16(config.DebugOptions.ProxyPort)
 			} else {
 				bf.WriteUint16(ci.Port)
 			}