Adding persons to a static cohort fails with a `500 Internal Server Error` in local development when the personhog path is active.

Bug Description

Bug description

Commit 5357ae3b695 introduced _insert_batch_via_personhog in posthog/models/cohort/cohort.py, which added a new ClickHouse SELECT query (_get_existing_ch_member_uuids) to deduplicate persons before insertion. This query runs without product/feature query tags, triggering UntaggedQueryError in DEBUG mode.

The error is DEBUG-only so it does not affect production.

How to reproduce

1. Run local dev environment with personhog enabled
2. Create a static cohort
3. Try to add persons to it via the UI or PATCH /api/cohort/:id/add_persons
4. Observe 500 Internal Server Error with traceback ending at posthog/models/cohort/cohort.py:848

Additional context

posthog.clickhouse.client.execute.UntaggedQueryError: sync_execute called with missing query tags: product, feature
  File "posthog/models/cohort/cohort.py", line 848, in _get_existing_ch_member_uuids

Root cause: _get_existing_ch_member_uuids calls sync_execute before insert_static_cohort (which already sets its own tags) gets a chance to run. Fix is to add tag_queries(product=ProductKey.COHORTS, feature=Feature.COHORT) in _insert_batch_via_personhog before the ClickHouse dedup check.

Debug info

- [ ] PostHog Cloud, Debug information: [please copy/paste from https://us.posthog.com/settings/project-details#variables or https://eu.posthog.com/settings/project-details#variables]
- [x] PostHog Hobby self-hosted with `docker compose`, version/commit: ddf3ea88199088713a822ef064e1e58f44c50717
- [ ] PostHog self-hosted with Kubernetes (deprecated, see [`Sunsetting Kubernetes support`](https://posthog.com/blog/sunsetting-helm-support-posthog)), version/commit: [please provide]

Start in posthog/models/cohort/cohort.py at _insert_batch_via_personhog and the _get_existing_ch_member_uuids call. Reproduce by enabling personhog and adding persons to a static cohort through the UI or PATCH /api/cohort/:id/add_persons, then inspect the ClickHouse query-tagging context. Done means the debug-only UntaggedQueryError and resulting 500 no longer occur.