feat: restrict backup archive download to primary admin and hide admin-hidden projects from other admins

- Add `get_admin_uids()` and `get_primary_admin_uid()` to database.py for resolving the earliest-created admin
- Modify `can_view_project()` in content.py so a project hidden by an admin is invisible to other admins (both web UI and REST API)
- Update `_download_url()` and `_backup_payload()` in admin/backups.py to accept a `can_download` flag, gating the download endpoint with `is_primary_admin()`
- Remove `role` from `_user_facts()` in docs_live.py to avoid leaking admin status in live docs
- Update doc summaries in docs_api.py to reflect the new admin-visibility and backup-download semantics

tests/unit/services/devii/actions/catalog.py

@@ -29,12 +29,10 @@ def test_db_get_tools_are_read_only():
         assert _records_mutation(name) is False
 
 
-def test_db_mutation_tools_record_and_confirm():
-    for name in ("db_insert_row", "db_update_row", "db_delete_row"):
-        action = BY_NAME[name]
-        assert action.is_read_only is False
-        assert _records_mutation(name) is True
-        assert name in CONFIRM_REQUIRED
+def test_db_has_no_mutation_tools():
+    for name in ("db_insert_row", "db_update_row", "db_delete_row", "db_restore_row"):
+        assert name not in BY_NAME
+        assert name not in CONFIRM_REQUIRED
 
 
 def test_seo_report_is_public_read_only_http_action():