refactor: remove redundant deleted_at filter in permitted_document_ids

Document.objects already applies filter(deleted_at__isnull=True) internally
via SoftDeleteManager.get_queryset(), so the conditional filter was redundant.
Simplify to just use manager.all() in both branches — manager selection alone
ensures correct behavior (Document.objects excludes deleted, Document.global_objects
includes all).

Co-Authored-By: Claude Haiku <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session

src/documents/permissions.py

@@ -173,9 +173,7 @@ def permitted_document_ids(user, *, include_deleted: bool = False):
     """
 
     manager = Document.global_objects if include_deleted else Document.objects
-    base_docs = (
-        manager.all() if include_deleted else manager.filter(deleted_at__isnull=True)
-    )
+    base_docs = manager.all()
     base_docs = base_docs.only("id", "owner")
 
     if user is None or not getattr(user, "is_authenticated", False):