perf(docs): Compress AI monitoring conversations images (#17148)

## DESCRIBE YOUR PR

Compress the two PNG images on the [AI monitoring conversations
page](https://docs.sentry.io/ai/monitoring/conversations/) using
pngquant (75-90 quality):

- `conversations-detail.png`: 971K → 261K (~73% reduction)
- `conversations-list.png`: 731K → 178K (~76% reduction)

Fixes https://linear.app/getsentry/issue/TET-2144

## IS YOUR CHANGE URGENT?

- [x] None: Not urgent, can wait up to 1 week+

## SLA

- Teamwork makes the dream work, so please add a reviewer to your PRs.
- Please give the docs team up to 1 week to review your PR unless you've
added an urgent due date to it.
Thanks in advance for your help!

## PRE-MERGE CHECKLIST

- [ ] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter
experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs
team](https://github.com/orgs/getsentry/teams/docs)

Co-authored-by: Claude <noreply@anthropic.com>

Author: obostjancic