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/note-editor/note-editor-toolbar.tsx

@@ -668,7 +668,7 @@ export function NoteEditorToolbar({ mode, onClose, onToggleAttachments, attachme
               title={voiceState === 'listening'
                 ? (t('editor.voiceStop') || 'Arrêter la dictée')
                 : (t('editor.voiceStart') || 'Dicter du texte')}
-              aria-label={voiceState === 'listening' ? 'Stop voice' : 'Start voice'}
+              aria-label={voiceState === 'listening' ? (t('richTextEditor.stopVoice') || 'Stop voice') : (t('richTextEditor.startVoice') || 'Start voice')}
               onClick={toggleVoice}
               className={cn(
                 'p-1.5 rounded-full border transition-all',