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>

tests/Feature/Jobs/PublishPostJobTest.php

@@ -60,6 +60,20 @@ test('it reverts to draft when no publisher supports the post type', function ()
         ->publish_error->toContain('No publisher available');
 });
 
+test('it skips a duplicate job for a post no longer in publishing state', function () {
+    Http::fake([
+        '*/wp-json/wp/v2/posts' => Http::response(['link' => 'https://wp.example.com/post'], 201),
+    ]);
+
+    $site = Site::factory()->wordpress()->create();
+    $post = Post::factory()->create(['site_id' => $site->id, 'type' => 'blog', 'title' => 'Hi', 'status' => 'published', 'published_url' => 'https://wp.example.com/already-there']);
+
+    (new PublishPostJob($post->id))->handle(app(PublisherManager::class));
+
+    Http::assertNothingSent();
+    expect($post->fresh()->published_url)->toBe('https://wp.example.com/already-there');
+});
+
 test('it publishes a reddit post via the sidecar', function () {
     Process::fake([
         '*' => Process::result(output: json_encode(['success' => true, 'url' => 'https://reddit.com/r/test/comments/abc'])),