- _group_int_doc_ids: use type(value) is not int instead of isinstance,
since bool is an int subclass and would otherwise stringify to
"True"/"False" and corrupt legacy payloads on backfill.
- Replace doc_id.isdigit() guards in 5 boundary sites
(api/visualization, auth/viz_routes, search/context note/news_item/
deck_card branches) with a shared is_valid_nextcloud_doc_id helper
that rejects "0", leading zeros, and Unicode digit classes
(superscripts, Arabic-Indic, Devanagari) which pass isdigit() but
cannot be valid MySQL AUTO_INCREMENT IDs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
