fix: only mark contact as messaged after initial

[ajohn25]

Description

This updates message sending so that the behavior of updating campaign_contact.message_status reflects the most common interpretation of how this should work by admins:

1. After an initial message is sent (the previous message_status is needsMessage), the status should be updated to messaged
2. Any other time a Spoke user sends a message, the status should be updated to "active conversation" (convo)

Edit: It's possible to send a message to a contact marked as messaged via Message Review - in this case we want to keep the messaged status

Motivation and Context

See context for bug find here: https://withtheranks.slack.com/archives/C01L3B18S10/p1723131234467449?thread_ts=1723060316.173739&cid=C01L3B18S10

How Has This Been Tested?

This has been tested locally

Screenshots (if appropriate):

Documentation Changes

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have included updates for the documentation accordingly.