feat(zdeploy): print 'Last deployed at' as the final line of a run

Scroll to the bottom of a deploy and you can see how long ago it happened,
without digging through the log or checking the server.

Placed after Stop-ZTracking so it is genuinely the last line, below the
token-tracking footer. Only reached on success - a failed deploy throws out of
the dispatch loop, so this never claims a deploy that did not happen. Prints
once per run rather than per project, so 'zdeploy all' ends with a single
timestamp.

24-hour clock (MM/dd/yyyy HH:mm:ss): the requested format carried no AM/PM
marker, and 24-hour is unambiguous for judging elapsed time at a glance.

CHECKSUMS.txt regenerated, since changing a covered script invalidates it.

CHECKSUMS.txt

@@ -8,7 +8,7 @@ c336a61cb8563736bd6550671d7dc90b14702a43f25a97b1ac15ffd64605fbf6  zbackup_ec2.cm
 20e6282901a919aa32ea717c739ba2dc9657426dff860f0e5fce201edefd99da  zchecksums.cmd
 692b7b0ff9e51e5d9b880358b33c54d2db4f967297a5350e154df1ce6f06ebc6  zchecksums.ps1
 b56085112e7c573926a70a58872163b71416d58ce91ea7114b1f5de5fc96c982  zdeploy.cmd
-8f52b2114c8d84e397b7a4f4e1f45ea7201c59fe3e1b4147fa08ad26d0325035  zdeploy.ps1
+f7bfab1bd07e86f05d4ae61ff9ab0df20e7273b7c2096c8d5945b477d84d85cd  zdeploy.ps1
 fa817d3bd7bba98b03b411d3c5a82b210d3cca316ac0c9785afa5b4ac5fe0766  zec2.cmd
 5f70432af23df3459a98d9ad6a0da723783f2269dd5f5ab8ecdd6366ebc84942  zec2.ps1
 4df94eda29b6f5b2cb6bfa63e0add4d90ea24d936305f36a69988e8dd5d69154  zec2_rotatekeys.cmd

zdeploy.ps1

@@ -643,3 +643,9 @@ foreach ($key in $Projects) {
     }
 }
 Stop-ZTracking
+
+# Last line of the run, after the tracking footer: scroll to the bottom and you
+# can see how long ago this deployed. Only reached on success - a failed deploy
+# throws out of the loop above, so this never claims a deploy that didn't happen.
+Write-Host ""
+Write-Host ("Last deployed at {0}" -f (Get-Date -Format "MM/dd/yyyy HH:mm:ss")) -ForegroundColor Cyan