improve: add warning logs to null guards and fix transferDevice error handling

- Add warning/debug logs to all null guard patterns (if (!x) return/continue)
  so that when these guards fire, the reason is visible in logs instead of
  being silently swallowed
- Fix jid-utils.ts transferDevice: throw Error instead of returning empty
  string '' which could propagate as an invalid JID
- process-message.ts: warn on creds.me missing, reactionKey missing,
  creationMsgKey missing, eventCreatorPn missing
- chats.ts: warn on sendPresenceUpdate/handlePresenceUpdate missing values
- event-buffer.ts: debug on chat/contact/group update missing id
- socket.ts: debug on sessionStartTime not set
- communities.ts: debug on dirty node not found
- libsignal.ts: warn on bulk migration jidDecode failure

https://claude.ai/code/session_01XaA7GwNaB6azTHFYQ8WEpB

src/Utils/process-message.ts

@@ -288,6 +288,7 @@ const processMessage = async (
 ) => {
 	const meUser = creds.me
 	if (!meUser) {
+		logger?.warn({ messageKey: message.key }, 'processMessage: creds.me not set, skipping message')
 		return
 	}
 
@@ -548,6 +549,7 @@ const processMessage = async (
 	} else if (content?.reactionMessage) {
 		const reactionKey = content.reactionMessage.key
 		if (!reactionKey) {
+			logger?.warn({ messageKey: message.key }, 'processMessage: reactionMessage.key missing, skipping')
 			return
 		}
 
@@ -565,6 +567,7 @@ const processMessage = async (
 		const encEventResponse = content.encEventResponseMessage
 		const creationMsgKey = encEventResponse.eventCreationMessageKey
 		if (!creationMsgKey) {
+			logger?.warn({ messageKey: message.key }, 'processMessage: eventCreationMessageKey missing, skipping')
 			return
 		}
 
@@ -580,6 +583,7 @@ const processMessage = async (
 					? await signalRepository.lidMapping.getPNForLID(eventCreatorKey)
 					: eventCreatorKey
 				if (!eventCreatorPn) {
+					logger?.warn({ messageKey: message.key, eventCreatorKey }, 'processMessage: eventCreatorPn missing, skipping')
 					return
 				}