- Create 'type MessageType int' in pkg/irc/numerics.go
- Type all Rpl*/Err* numeric constants as MessageType
- Add Name() method returning the standard IRC name (e.g. RPL_WELCOME)
- Add String() method returning zero-padded numeric (e.g. 001)
- Update enqueueNumeric/respondIRCError to accept MessageType
- Update internal/db to use MessageType conversion for Name() calls
- Change names map key type from int to MessageType
Refs #52