feat: add inbound username support and USync username protocol (#382)

* feat: add inbound username support and USync username protocol

Aligns with Baileys upstream PR #2480. WhatsApp is rolling out an
inbound username field that maps to the user's LID. This change is
purely additive — it captures and propagates the new optional field
through types, decoders, USync queries, and group/contact events.

Skipped intentionally to preserve InfiniteAPI's LID/PN customization:
- handleGroupNotification in messages-recv.ts (custom LID->PN flow on
  groups.upsert / participants.map). Username for these specific
  events still flows via process-message's emitParticipantsUpdate
  (reads message.key.participantUsername added in decode-wa-message).

Carousel/buttons code (messages.ts, messages-send.ts) untouched.

Co-Authored-By: Renato Alcara

src/Types/Message.ts

@@ -19,7 +19,9 @@ export type WAContactMessage = proto.Message.IContactMessage
 export type WAContactsArrayMessage = proto.Message.IContactsArrayMessage
 export type WAMessageKey = proto.IMessageKey & {
 	remoteJidAlt?: string
+	remoteJidUsername?: string
 	participantAlt?: string
+	participantUsername?: string
 	server_id?: string
 	addressingMode?: string
 	isViewOnce?: boolean // TODO: remove out of the message key, place in WebMessageInfo