fix: add pastParticipants to HistorySync with LID normalization and deduplication (#303)

Two bugs fixed compared to prior implementation:

1. history.ts — normalize userJid LID→PN
   pastParticipants[].userJid may arrive as a LID identifier (e.g. "46802258641027@lid").
   The consumer expects a phone number. After building the lidPnMap from conversations
   and phoneNumberToLidMappings, each userJid is resolved to its PN equivalent.
   If the mapping is not available the original value is preserved (no data loss).

2. event-buffer.ts — deduplicate by groupJid + userJid across chunks
   Multiple HistorySync chunks can contain the same group. The previous approach
   concatenated blindly, producing duplicate entries. Now a keyed map
   { [groupJid]: IPastParticipant[] } is used so each group appears once and
   each participant within a group appears at most once.

Types updated (Events.ts):
   - messaging-history.set event includes pastParticipants?: IPastParticipants[]
   - BufferedEventData.historySets.pastParticipants typed as keyed map

src/Utils/history.ts

@@ -374,10 +374,25 @@ export const processHistoryMessage = (item: proto.IHistorySync, logger?: ILogger
 	// Convert Map back to array for return
 	const lidPnMappings = Array.from(lidPnMap.values())
 
+	// Normalize pastParticipants: resolve LID userJids → PN so the consumer always
+	// receives a phone number, never an opaque LID identifier.
+	// Uses the lidPnMap built above (populated from phoneNumberToLidMappings + conversations).
+	// If a LID cannot be resolved, the original value is kept rather than dropping the participant.
+	const pastParticipants: proto.IPastParticipants[] = (item.pastParticipants ?? []).map(group => ({
+		groupJid: group.groupJid,
+		pastParticipants: (group.pastParticipants ?? []).map(participant => {
+			const userJid = participant.userJid
+			if (!userJid || !isAnyLidUser(userJid)) return participant
+			const mapping = lidPnMap.get(jidNormalizedUser(userJid))
+			return mapping?.pn ? { ...participant, userJid: mapping.pn } : participant
+		})
+	}))
+
 	return {
 		chats,
 		contacts,
 		messages,
+		pastParticipants,
 		lidPnMappings,
 		syncType: item.syncType,
 		progress: item.progress