fix: revert ?? '' and defensive null checks across Socket files

PRs 124-129 replaced TypeScript non-null assertions (!) with optional
chaining (?.) and empty string defaults (?? ''). While defensive
programming is usually good, in Signal protocol and WhatsApp binary
node handling code these changes caused:

- Malformed JIDs with empty user components (e.g. @s.whatsapp.net)
- Silent device enumeration failures (messages skip recipients)
- Wrong own-device detection (message routing errors)
- Broken prekey count handling (prekey uploads silently skipped)
- Wrong retry count tracking in Signal protocol

These empty-string defaults are dangerous because Signal session
lookups fail for malformed JIDs, causing "SessionError: No sessions".

Reverted to original Baileys pattern using non-null assertions (!)
which match the upstream reference (infinitezap/Teste_InfiniteAPI).

Files fixed: messages-send.ts, messages-recv.ts, socket.ts, chats.ts,
groups.ts, communities.ts, business.ts

https://claude.ai/code/session_01XaA7GwNaB6azTHFYQ8WEpB

src/Socket/chats.ts

@@ -1107,8 +1107,8 @@ export const makeChatsSocket = (config: SocketConfig) => {
 		ev.emit('messages.upsert', { messages: [msg], type })
 
 		if (!!msg.pushName) {
-			let jid = msg.key.fromMe ? (authState.creds.me?.id ?? '') : msg.key.participant || msg.key.remoteJid
-			jid = jidNormalizedUser(jid ?? '')
+			let jid = msg.key.fromMe ? authState.creds.me!.id : msg.key.participant || msg.key.remoteJid
+			jid = jidNormalizedUser(jid!)
 
 			if (!msg.key.fromMe) {
 				ev.emit('contacts.update', [{ id: jid, notify: msg.pushName, verifiedName: msg.verifiedBizName! }])