feat: persist script feature toggles to backend

Features (scroll, 404, outbound, downloads, frustration, storage, ttl)
are saved to site.script_features JSONB column on every toggle change.
Values are read from the site object on load.

lib/api/sites.ts

@@ -23,6 +23,8 @@ export interface Site {
   hide_unknown_locations?: boolean
   // Data retention (months); 0 = keep forever
   data_retention_months?: number
+  // Script feature toggles
+  script_features?: Record<string, unknown>
   is_verified?: boolean
   created_at: string
   updated_at: string
@@ -49,6 +51,8 @@ export interface UpdateSiteRequest {
   collect_screen_resolution?: boolean
   // Bot and noise filtering
   filter_bots?: boolean
+  // Script feature toggles
+  script_features?: Record<string, unknown>
   // Hide unknown locations from stats
   hide_unknown_locations?: boolean
   // Data retention (months); 0 = keep forever