Gate scheduled automations and fail closed on per-model access for non-user roles (#26047)

Two lifecycle/authorization gaps let a deactivated (pending) account keep acting:

1. The background automation scheduler (execute_automation) rehydrated the owner by ID and
   dispatched the chat pipeline without re-checking the owner. A user later set to pending,
   or one whose features.automations permission was revoked, kept running scheduled
   automations on the operator's provider credentials, even though the HTTP create/update/run
   routes already gate on get_verified_user + features.automations. Re-gate the rehydrated
   owner before dispatch: require role user/admin and, for non-admins, the features.automations
   permission; otherwise record an error and skip the run.

2. check_model_access enforced per-model ACLs only for exactly role == 'user', so any other
   non-admin role (a pending principal) fell through and was granted access. Enforce for every
   non-admin role (admins still bypass), so the check fails closed (CWE-862, CWE-863).

Co-authored-by: rexpository <30176934+rexpository@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/open_webui/utils/access_control/__init__.py

@@ -321,7 +321,8 @@ async def check_model_access(
         return
 
     if model_info:
-        if user.role == 'user':
+        # Enforce for every non-admin role (including pending); never fail open.
+        if user.role != 'admin':
             from open_webui.models.access_grants import AccessGrants
 
             user_group_ids = {group.id for group in await Groups.get_groups_by_member_id(user.id)}