precache a user's default session replay listing view

Feature request

as your number of recordings and persons grows the initial query to load a page of recording results can get annoyingly slow

we could start running the query before you get to the replay page (and wait on its results if you visit the page before we've finished) so that the query appears faster than it really is

• when django starts a new session
• or when the front-end returns from idle and hits an API to tell us
• we run the session replay query that the user would run if they hit the page
• and cache the result
• so that when they navigate to replay the loading is almost instant
• would mean we run the query more than we need to since not everyone will visit replay
• and would mean we'd need to know the filters they have stored in local storage
• but for larger customers where the initial load can take many seconds this would probably be a great boost
• and we could opt in teams only when we see their list loading time is consistently greater than X seconds

Debug info

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

No files or tests are named. Start by tracing session startup in Django, the front-end idle-return API, and the session replay listing query, including how filters are stored in local storage. Done would require an agreed caching strategy, team opt-in threshold, and evidence that replay loads faster without unacceptable extra queries.