Guard PublishPostJob against duplicate/stale dispatches

Skip if the post is no longer status=publishing when the job runs, so
a stray duplicate (e.g. clicking Publish twice while no worker was
running) can't publish the same post to WordPress a second time.

Also root-caused a stuck-in-"publishing" post reported live: the
queue worker started manually last session was a bare background
process, not a real service, and had died. Replaced it with a
systemd unit (muninn-queue-worker.service, enabled + running) so
the Publish button keeps working across reboots/restarts.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/Jobs/PublishPostJob.php

@@ -27,6 +27,13 @@ class PublishPostJob implements ShouldQueue
             return;
         }
 
+        // A duplicate/stale job for a post already resolved by an earlier
+        // run of this same job (e.g. a double-dispatch while no worker was
+        // running) — skip it rather than risk publishing twice.
+        if ($post->status !== 'publishing') {
+            return;
+        }
+
         $publisher = $publishers->resolve($post);
 
         if (! $publisher) {