feat: implement WhatsApp connection and message metrics

Added tracking for all WhatsApp-related metrics:

Connection metrics:
- active_connections: Gauge tracking active connections (inc on open, dec on close)
- connection_attempts_total: Counter for connection attempts (success/failure)

Message metrics:
- messages_sent_total: Counter with type label (text, image, video, audio, etc)
- messages_received_total: Counter with type label
- history_sync_messages_total: Counter for history sync messages

Added helper functions in prometheus-metrics.ts:
- incrementActiveConnections(), decrementActiveConnections(), setActiveConnections()
- recordConnectionAttempt(status)
- recordMessageSent(type), recordMessageReceived(type)
- recordMessageRetry(type), recordMessageFailure(type, reason)
- setMessagesQueued(count, priority)
- recordHistorySyncMessages(count)

src/Utils/process-message.ts

@@ -16,7 +16,7 @@ import type {
 	WAMessage,
 	WAMessageKey
 } from '../Types'
-import { metrics } from './prometheus-metrics.js'
+import { metrics, recordHistorySyncMessages } from './prometheus-metrics.js'
 import { WAMessageStubType } from '../Types'
 import { getContentType, normalizeMessageContent } from '../Utils/messages'
 import {
@@ -353,6 +353,11 @@ const processMessage = async (
 						isLatest: histNotification.syncType !== proto.HistorySync.HistorySyncType.ON_DEMAND ? isLatest : undefined,
 						peerDataRequestSessionId: histNotification.peerDataRequestSessionId
 					})
+
+					// Record history sync metrics
+					if (data.messages?.length) {
+						recordHistorySyncMessages(data.messages.length)
+					}
 				}
 
 				break