Incoming messages display the sender's incorrect device time

• I have searched open and closed issues for duplicates
• I am submitting a bug report for existing functionality that does not work as intended
• This isn't a feature request or a discussion topic

Bug description

When the sender's iOS system clock is incorrect, an incoming message is
displayed on the recipient's device using the sender's incorrect local time.

For example, if the sender's clock is two minutes behind, a message that is sent
and received immediately appears to the recipient as if it were sent two minutes
ago.

This is reproducible with clock offsets smaller than the current excessive
clock-skew threshold.

Steps to reproduce

• Use two Signal accounts on two devices: Device A as the sender and Device B as the recipient.
• On Device A, disable “Set Automatically” under iOS Settings > General > Date & Time.
• Set Device A's clock approximately two minutes behind the actual time.
• Open Signal on Device A and send a message to Device B.
• Immediately open the conversation on Device B.
• Observe the timestamp displayed below the incoming message.

Start by reproducing the two-device scenario described in the issue, then trace how an incoming message's timestamp is selected and displayed in Signal-iOS. No file or test is named, so read around the incoming-message timestamp path first. Done means a sender clock offset of about two minutes no longer makes the recipient see the message as older than it is.