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/components/note-peek/use-note-peek.ts

@@ -0,0 +1,60 @@
+'use client'
+
+import { useState, useCallback, useEffect } from 'react'
+import { getNoteById } from '@/app/actions/notes'
+import type { Note } from '@/lib/types'
+import {
+  NOTE_PEEK_OPEN_EVENT,
+  NOTE_PEEK_CLOSE_EVENT,
+  type NotePeekOpenDetail,
+} from '@/lib/note-peek-sync'
+
+interface UseNotePeekOptions {
+  selfNoteId?: string
+}
+
+export function useNotePeek(opts: UseNotePeekOptions = {}) {
+  const { selfNoteId } = opts
+  const [note, setNote] = useState<Note | null>(null)
+  const [blockId, setBlockId] = useState<string | undefined>(undefined)
+  const [loading, setLoading] = useState(false)
+  const [isOpen, setIsOpen] = useState(false)
+
+  const open = useCallback(async (targetNoteId: string, targetBlockId?: string) => {
+    if (selfNoteId && targetNoteId === selfNoteId) return
+    setLoading(true)
+    setIsOpen(true)
+    setBlockId(targetBlockId)
+    try {
+      const fetched = await getNoteById(targetNoteId)
+      if (fetched) setNote(fetched)
+    } catch {
+      // silent
+    } finally {
+      setLoading(false)
+    }
+  }, [selfNoteId])
+
+  const close = useCallback(() => {
+    setIsOpen(false)
+    setNote(null)
+    setBlockId(undefined)
+  }, [])
+
+  useEffect(() => {
+    const onOpen = (e: Event) => {
+      const detail = (e as CustomEvent<NotePeekOpenDetail>).detail
+      if (!detail) return
+      void open(detail.noteId, detail.blockId)
+    }
+    const onClose = () => close()
+    window.addEventListener(NOTE_PEEK_OPEN_EVENT, onOpen)
+    window.addEventListener(NOTE_PEEK_CLOSE_EVENT, onClose)
+    return () => {
+      window.removeEventListener(NOTE_PEEK_OPEN_EVENT, onOpen)
+      window.removeEventListener(NOTE_PEEK_CLOSE_EVENT, onClose)
+    }
+  }, [open, close])
+
+  return { note, blockId, loading, isOpen, open, close }
+}