feat(notes): liens internes, onglet Réseau, living blocks et consentement IA

Rend les liens entre notes visibles et persistants (sync NoteLink au save, auto-save, graphe réseau rafraîchi), ajoute living blocks, Memory Echo, recherche globale, consentement IA explicite et consolide les prototypes design en architectural-grid.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/app/api/blocks/embed/route.ts

@@ -0,0 +1,44 @@
+import { NextRequest, NextResponse } from 'next/server'
+import prisma from '@/lib/prisma'
+import { auth } from '@/auth'
+
+// POST /api/blocks/embed
+// Body: { sourceNoteId, blockId, targetNoteId }
+export async function POST(request: NextRequest) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  const body = await request.json()
+  const { sourceNoteId, blockId, targetNoteId } = body
+
+  if (!sourceNoteId || !blockId || !targetNoteId) {
+    return NextResponse.json({ error: 'sourceNoteId, blockId and targetNoteId are required' }, { status: 400 })
+  }
+
+  // Verify both notes belong to the user
+  const [sourceNote, targetNote] = await Promise.all([
+    prisma.note.findFirst({ where: { id: sourceNoteId, userId: session.user.id } }),
+    prisma.note.findFirst({ where: { id: targetNoteId, userId: session.user.id } }),
+  ])
+
+  if (!sourceNote || !targetNote) {
+    return NextResponse.json({ error: 'Note not found or unauthorized' }, { status: 404 })
+  }
+
+  // Upsert — avoid duplicate refs
+  const existing = await prisma.liveBlockRef.findFirst({
+    where: { sourceNoteId, blockId, targetNoteId },
+  })
+
+  if (existing) {
+    return NextResponse.json({ id: existing.id, created: false })
+  }
+
+  const ref = await prisma.liveBlockRef.create({
+    data: { sourceNoteId, blockId, targetNoteId },
+  })
+
+  return NextResponse.json({ id: ref.id, created: true })
+}