- Always-visible 'Catégorie IA' block in EventDetail (view + edit mode)
- Dropdown lists all EventCategories; selecting one instantly saves sub_type
and updates category type via PUT (no need to enter full edit mode)
- Shows matched category description + default impacts preview (ticker chips
with direction arrows and sensitivity %)
- Edit mode: category dropdown also auto-sets the category type field
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>