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/social/models.py

@@ -3,6 +3,29 @@ from django.db import models
 
 from core.models import TimeStampedModel, UUIDPrimaryKeyModel
 
+_GENERIC_ACCOUNT_LABELS = frozenset(
+    {
+        "linkedin member",
+        "instagram account",
+        "facebook page",
+    }
+)
+
+
+def is_generic_account_label(label: str) -> bool:
+    """True when OAuth left a placeholder or unreadable name."""
+    text = (label or "").strip()
+    if not text:
+        return True
+    lowered = text.lower()
+    if lowered in _GENERIC_ACCOUNT_LABELS:
+        return True
+    if lowered.startswith("page ") and text.split()[-1].isdigit():
+        return True
+    if text.startswith("urn:"):
+        return True
+    return False
+
 
 class Platform(models.TextChoices):
     FACEBOOK = "facebook", "Facebook"
@@ -54,6 +77,22 @@ class SocialAccount(UUIDPrimaryKeyModel, TimeStampedModel):
     def __str__(self) -> str:
         return f"{self.platform}: {self.label}"
 
+    @property
+    def display_name(self) -> str:
+        return (self.label or "").strip() or self.get_platform_display()
+
+    @staticmethod
+    def resolve_label(existing: "SocialAccount | None", incoming: str) -> str:
+        """Keep a custom rename; otherwise take the OAuth name."""
+        incoming = (incoming or "").strip()[:120]
+        if existing is not None and not is_generic_account_label(existing.label):
+            return existing.label
+        if incoming:
+            return incoming
+        if existing and existing.label:
+            return existing.label
+        return "Account"
+
 
 class SocialPost(UUIDPrimaryKeyModel, TimeStampedModel):
     class Status(models.TextChoices):