Allow repeated Update activities for post edits

The dedup guard was blocking legitimate edits after the first Update.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

services/federation_publish.py

@@ -49,8 +49,6 @@ async def try_publish(
     if existing:
         if activity_type == "Create" and existing.activity_type != "Delete":
             return  # already published (allow re-Create after Delete/unpublish)
-        if activity_type == "Update" and existing.activity_type == "Update":
-            return  # already updated (Ghost fires duplicate webhooks)
         if activity_type == "Delete" and existing.activity_type == "Delete":
             return  # already deleted
     elif activity_type in ("Delete", "Update"):