Perf: batch guardian permission assignment in bulk-edit

bulk_edit.set_permissions and BulkEditObjectPermissionsView both
looped documents/objects and called set_permissions_for_object per
object, which itself calls guardian's assign_perm/remove_perm once
per (object, user) pair -- ~10-20+ queries per object, scaling with
selection size.

Added set_permissions_for_objects, a bulk equivalent that resolves
existing permission holders once across the whole batch (not once per
object) and applies changes with a small, batch-size-independent
number of queries per action instead of one per (object, user) pair.

Deliberately does not use guardian's queryset-aware assign_perm:
passing a list as the target routes to bulk_assign_perm, which skips
creating a direct permission row for anyone who already has the
permission via ANY group membership (checked via
ObjectPermissionChecker.has_perm, which is group-inheritance-aware) --
unlike the single-object assign_perm this replaces, which always
ensures a direct row via get_or_create. Losing that guarantee would
mean a later revocation of the group's grant silently strips access
an admin explicitly asked to be direct. Bulk-creates rows straight
against UserObjectPermission/GroupObjectPermission instead
(ignore_conflicts=True, relying on the existing (identity, permission,
object_pk) unique constraint), which preserves the original semantics
exactly while still batching every object and identity into one query
per action. Also raises Permission.DoesNotExist for an unrecognized
action name instead of silently no-op-ing, matching the original
per-object path -- BulkEditObjectsSerializer never actually validates
action keys against the raw client-supplied permissions dict, so this
is reachable from client input, not just internal callers.

Verified via CaptureQueriesContext: query count is now identical at 5
vs. 50 documents/objects (was 1,123 queries for 20 documents on the
Document path, 2,806 for 50 tags on the BulkEditObjectPermissionsView
path, both now flat). Full documents test suite green (2,148 passed,
1 skipped).

src/documents/views.py

@@ -178,7 +178,7 @@ from documents.permissions import has_perms_owner_aware
 from documents.permissions import has_system_status_permission
 from documents.permissions import permitted_document_ids
 from documents.permissions import permitted_object_ids
-from documents.permissions import set_permissions_for_object
+from documents.permissions import set_permissions_for_objects
 from documents.plugins.date_parsing import get_date_parser
 from documents.schema import generate_object_with_permissions_schema
 from documents.search import SearchHit
@@ -4910,12 +4910,11 @@ class BulkEditObjectsView(PassUserMixin):
                     qs_owner_update.update(owner=owner)
 
                 if "permissions" in serializer.validated_data:
-                    for obj in qs:
-                        set_permissions_for_object(
-                            permissions=permissions,
-                            object=obj,
-                            merge=merge,
-                        )
+                    set_permissions_for_objects(
+                        permissions=permissions,
+                        objects=qs,
+                        merge=merge,
+                    )
 
             except Exception as e:
                 logger.warning(