feat: configurable stop grace period for applications

Adds stop_grace_period to application settings (seconds, 1-3600, default 30).
Used in place of the hardcoded docker stop -t 30 in the four places that
stop application containers: rolling update shutdown, manual stop, stop on
another server, and preview deployment stop.

Non-positive values fall back to the default via ($val > 0) ? $val : default,
with tests covering 0 and -10 so the cast does not blow up if a bad value
ever lands in the db.

Picks up Jack Coy's work from #7125 which went dormant. His commits are
squashed here with credit below.

Co-authored-by: Jack Coy <jackman3000@gmail.com>

app/Actions/Application/StopApplication.php

@@ -36,10 +36,13 @@ class StopApplication
                     : getCurrentApplicationContainerStatus($server, $application->id, 0);
 
                 $containersToStop = $containers->pluck('Names')->toArray();
+                $timeout = ($application->settings->stop_grace_period > 0)
+                    ? $application->settings->stop_grace_period
+                    : DEFAULT_STOP_GRACE_PERIOD_SECONDS;
 
                 foreach ($containersToStop as $containerName) {
                     instant_remote_process(command: [
-                        "docker stop -t 30 $containerName",
+                        "docker stop --time=$timeout $containerName",
                         "docker rm -f $containerName",
                     ], server: $server, throwError: false);
                 }