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

docker-compose.yml

@@ -67,7 +67,6 @@ services:
 
   worker:
     build: .
-    profiles: ["worker"]
     entrypoint: ["/worker-entrypoint.sh"]
     volumes:
       - ./site:/app/site
@@ -77,6 +76,8 @@ services:
       DJANGO_DEBUG: ${DJANGO_DEBUG:-true}
       DJANGO_ALLOWED_HOSTS: ${DJANGO_ALLOWED_HOSTS:-localhost,127.0.0.1,0.0.0.0}
       DATABASE_URL: ${COMPOSE_DATABASE_URL:-postgres://monica_site:monica_site@db:5432/monica_site}
+      PUBLIC_SITE_URL: ${PUBLIC_SITE_URL:-http://127.0.0.1:8000}
+      DISPATCH_DUE_INTERVAL_SECONDS: ${DISPATCH_DUE_INTERVAL_SECONDS:-15}
       EMAIL_HOST: ${EMAIL_HOST:-mail.smtp2go.com}
       EMAIL_HOST_USER: ${EMAIL_HOST_USER:-}
       EMAIL_HOST_PASSWORD: ${EMAIL_HOST_PASSWORD:-}