fix(ux-audit): CRITICAL + HIGH fixes — a11y, reduced-motion, forms, keyboard nav

Global (globals.css):
- prefers-reduced-motion: désactive toutes les animations/transitions
- focus-visible:ring global sur tous les éléments interactifs

Search modal:
- role="dialog" + aria-modal="true" + aria-label
- onClick backdrop ferme la modale

Insights peek:
- DOMPurify.sanitize() sur dangerouslySetInnerHTML (XSS fix)

Login form:
- autoComplete="email" / "current-password"
- htmlFor sur tous les labels

Register form:
- autoComplete="name" / "email" / "new-password"
- htmlFor sur tous les labels

GridCard (notes-list-views):
- Actions visibles sur mobile (opacity-100 sm:opacity-0)
- aria-sort sur colonne triable
- role="button" + tabIndex + onKeyDown sur lignes table

Editorial view:
- role="button" + tabIndex + onKeyDown sur articles
- Menu trigger aria-label + visible mobile

Toolbar:
- aria-label voice i18n

memento-note/components/search-modal.tsx

@@ -409,7 +409,13 @@ export function SearchModal({ isOpen, onClose }: SearchModalProps) {
   if (!isOpen) return null
 
   return (
-    <div className="fixed inset-0 bg-black/40 dark:bg-black/60 backdrop-blur-sm flex items-center justify-center z-[200] p-4 sm:p-6 select-none">
+    <div
+      className="fixed inset-0 bg-black/40 dark:bg-black/60 backdrop-blur-sm flex items-center justify-center z-[200] p-4 sm:p-6 select-none"
+      role="dialog"
+      aria-modal="true"
+      aria-label="Recherche"
+      onClick={(e) => { if (e.target === e.currentTarget) onClose() }}
+    >
       <motion.div
         initial={{ opacity: 0, scale: 0.98, y: 8 }}
         animate={{ opacity: 1, scale: 1, y: 0 }}