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/app/(main)/insights/page.tsx

@@ -28,6 +28,7 @@ import Link from 'next/link'
 import { getNoteById } from '@/app/actions/notes'
 import type { Note as NoteFull } from '@/lib/types'
 import { X, Maximize2 } from 'lucide-react'
+import DOMPurify from 'dompurify'
 
 const NetworkGraph = dynamic(
   () => import('@/components/network-graph').then(m => ({ default: m.NetworkGraph })),
@@ -934,7 +935,7 @@ export default function InsightsPage() {
                   <div
                     dir="auto"
                     className="prose prose-sm dark:prose-invert max-w-none text-ink dark:text-dark-ink [&_a]:text-blue-600 [&_blockquote]:border-l-blue-400"
-                    dangerouslySetInnerHTML={{ __html: peekNote.content }}
+                    dangerouslySetInnerHTML={{ __html: DOMPurify.sanitize(peekNote.content) }}
                   />
                 ) : (
                   <p className="text-sm text-concrete italic">—</p>