Mirror the existing issues state filter pattern: read state query param
(default "open"), pass it to ListAllPullRequests instead of hardcoded
"open", and add a state select widget to the pulls filter bar with
proper hx-include for HTMX partial reloads and infinite scroll.
Closesleeworks-agents/gitea-mobile#72
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>