Add "retry" button instead of deleting messages that failed to send

[taoeffect]

Problem

If a message fails to send, PR #1877 currently deletes it.

This can be a problem for users who wrote a long message and don't want to retype it.

Solution

Leave it grayed out and add a button or a link that says "resend message" to the message to try again.

• When the user clicks on it, make the link disappear to show that an attempt has been made to resend it
• If the message succeeds, make the message no longer grey and remove the "resend message" link
• If the message fails to send again, show the link again