This PR updates Facebook Messenger outbound tagging in Chatwoot to support Human Agent messaging when enabled. Previously, Facebook outbound text and attachment messages were always sent with: ``` messaging_type: MESSAGE_TAG tag: ACCOUNT_UPDATE ``` With this change, the tag is selected dynamically: ``` HUMAN_AGENT when ENABLE_MESSENGER_CHANNEL_HUMAN_AGENT is enabled ACCOUNT_UPDATE as fallback when the flag is disabled ```