Make forms interactive with HTMX:
1. Status update dropdown on task detail:
- hx-post='/tasks/:id/status'
- hx-swap='outerHTML' on the status badge
- No page reload needed
2. Filter form on /tasks:
- hx-get='/tasks' on form
- hx-push-url='true' to update browser URL
- hx-target='#task-list' to only replace the list