refactor: factorisation peek panel — NotePeekPanel réutilisable

Architecture:
- components/note-peek/use-note-peek.ts: hook (fetch + state + events)
- components/note-peek/note-peek-content.tsx: rendu markdown/richtext/KaTeX
- components/note-peek/note-peek-panel.tsx: panel (overlay + inline modes)
- components/note-peek/index.ts: exports
- lib/use-scroll-to-block.ts: utilitaire scroll vers data-id

insights/page.tsx:
- ~95 lignes (state + fetch + KaTeX useEffect + AnimatePresence) → 10 lignes
- peek.open(noteId) remplace handleNoteClick complexe
- <NotePeekPanel mode=overlay /> remplace tout le JSX du panel

NotePeekPanel gère:
- markdown (MarkdownContent) + richtext (DOMPurify + KaTeX lazy)
- RTL (slide gauche pour fa/ar)
- prefers-reduced-motion
- role=dialog + aria-modal (overlay mode)
- loading spinner
- bouton Maximize2 + X
- renderContent prop pour custom (éditeur read-only)

memento-note/lib/use-scroll-to-block.ts

@@ -0,0 +1,19 @@
+import { useEffect, useRef } from 'react'
+
+export function useScrollToBlock(
+  scrollRef: React.RefObject<HTMLElement | null>,
+  blockId: string | undefined,
+  deps: React.DependencyList,
+  delay = 450,
+) {
+  useEffect(() => {
+    if (!blockId || !scrollRef.current) return
+    const timer = window.setTimeout(() => {
+      const escaped = typeof CSS !== 'undefined' && CSS.escape ? CSS.escape(blockId) : blockId
+      const el = scrollRef.current?.querySelector(`[data-id="${escaped}"]`)
+      el?.scrollIntoView({ behavior: 'smooth', block: 'center' })
+    }, delay)
+    return () => window.clearTimeout(timer)
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [blockId, delay, ...deps])
+}