Featurebase messenger + changelog widget dominates client-side pageload cost on the lot detail route

Found while investigating TPTM-3215 (lot detail page perf audit). Not fixed as part of that PR — filing as a follow-up.

Evidence (Sentry spans dataset, tptm project, 7d/30d windows, lot detail route):

• ~6 Featurebase requests fire per pageload:
• sdk.js — p95 1.17s
• widget/config — p95 1.46s
• changelog/widget/config — p95 1.30s
• conversations/list — p95 1.33s
• tickets/list
• 2 CSS files
• This is the single biggest client-side contributor to pageload time on the route — bigger than any of the route's own data fetching.

Suggestion: defer Featurebase SDK boot behind an idle callback or first user interaction instead of loading it eagerly on every app pageload.

Related to TPTM-3215.