Social composer: send now and rename messy account names (#6)

## Summary
Closes #5.
- Composer can **Send now** without a schedule time (Schedule and Save draft still available)
- Account names wrap and show the platform id so a bad OAuth label is still readable
- Social accounts page can rename the display name; re-auth keeps a custom name instead of overwriting it with a placeholder
- Worker polls `dispatch_due` every 15s so scheduled campaigns and social posts fire without a manual command; local `docker compose up` now starts the worker

## Test plan
- [ ] Open Social → Compose: confirm **Send now**, **Schedule**, and **Save draft** buttons (no combined Save / publish)
- [ ] Send now with a connected account and caption → post queues immediately, no datetime required
- [ ] Schedule with a datetime → post is scheduled; Schedule with a blank time → validation error
- [ ] Composer account list shows full name plus external id, wrapping if the name is long
- [ ] Social accounts → rename a messy label → new name shows in composer without reconnecting
- [ ] Re-authorize an account that was renamed → custom name is kept
- [ ] Rebuild and start compose (`docker compose up --build`) so the **worker** service is running
- [ ] Schedule a social post ~2 minutes ahead → after due time, worker logs `Enqueued N due item(s).` and the post leaves Scheduled (published or failed)
- [ ] `docker compose logs -f worker` shows `Polling due scheduled work every 15s.`

Reviewed-on: #6

site/core/tests.py

@@ -1,5 +1,13 @@
+from datetime import timedelta
+from io import StringIO
+from unittest.mock import patch
+
+from django.core.management import call_command
 from django.test import Client, TestCase, override_settings
 from django.urls import reverse
+from django.utils import timezone
+
+from social.models import SocialPost
 
 
 class HealthzTests(TestCase):
@@ -27,3 +35,43 @@ class PublicSmokeTests(TestCase):
         client = Client()
         self.assertEqual(client.get(reverse("public:about")).status_code, 200)
         self.assertEqual(client.get(reverse("public:contact")).status_code, 200)
+
+
+class DispatchDueTests(TestCase):
+    def test_enqueues_past_scheduled_social_post(self):
+        post = SocialPost.objects.create(
+            body="Open house",
+            status=SocialPost.Status.SCHEDULED,
+            scheduled_for=timezone.now() - timedelta(minutes=5),
+        )
+        mock_task = patch(
+            "core.management.commands.dispatch_due.publish_social_post"
+        ).start()
+        self.addCleanup(patch.stopall)
+        out = StringIO()
+        call_command("dispatch_due", stdout=out)
+        post.refresh_from_db()
+        self.assertEqual(post.status, SocialPost.Status.QUEUED)
+        mock_task.enqueue.assert_called_once_with(post_id=str(post.pk))
+        self.assertIn("Enqueued 1 due item(s).", out.getvalue())
+
+    def test_skips_future_scheduled_social_post(self):
+        post = SocialPost.objects.create(
+            body="Later",
+            status=SocialPost.Status.SCHEDULED,
+            scheduled_for=timezone.now() + timedelta(hours=1),
+        )
+        mock_task = patch(
+            "core.management.commands.dispatch_due.publish_social_post"
+        ).start()
+        self.addCleanup(patch.stopall)
+        call_command("dispatch_due", stdout=StringIO())
+        post.refresh_from_db()
+        self.assertEqual(post.status, SocialPost.Status.SCHEDULED)
+        mock_task.enqueue.assert_not_called()
+
+    def test_quiet_when_nothing_due(self):
+        out = StringIO()
+        call_command("dispatch_due", stdout=out)
+        self.assertEqual(out.getvalue(), "")
+