adjust registered by to managed by on db aslo remove url and api key on adding sites for gm

backend/apps/sync/models.py

@@ -17,20 +17,22 @@ class ActiveSite(models.Model):
     name = models.CharField(max_length=120)
     api_base_url = models.URLField(
         max_length=255,
-        help_text="Site API root including /api/v1, e.g. https://site.example/api/v1",
+        blank=True,
+        default="",
+        help_text="Optional site API root including /api/v1 (for outbound sync/push)",
     )
     api_key = models.CharField(
         max_length=255,
         blank=True,
         help_text="X-API-Key for pulling from the site API (keep server-side only)",
     )
-    registered_by = models.ForeignKey(
+    managed_by = models.ForeignKey(
         settings.AUTH_USER_MODEL,
         null=True,
         blank=True,
         on_delete=models.SET_NULL,
-        related_name="registered_active_sites",
-        help_text="GM / GM Admin who added this site dashboard URL",
+        related_name="managed_active_sites",
+        help_text="GM / GM Admin who manages this active site",
     )
     is_active = models.BooleanField(default=True)
     last_synced_at = models.DateTimeField(null=True, blank=True)