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/lib/consent/ai-consent-client.ts

@@ -0,0 +1,39 @@
+const LOCAL_STORAGE_KEY = 'memento-ai-consent-v1'
+
+/**
+ * Reads the persistent AI processing consent value from local storage.
+ * Returns true if consented, false if rejected or not set.
+ */
+export function getLocalStorageAiConsent(): boolean {
+  if (typeof window === 'undefined') return false
+  try {
+    const val = localStorage.getItem(LOCAL_STORAGE_KEY)
+    return val === 'true'
+  } catch {
+    return false
+  }
+}
+
+/**
+ * Writes the persistent AI processing consent value to local storage.
+ */
+export function setLocalStorageAiConsent(value: boolean): void {
+  if (typeof window === 'undefined') return
+  try {
+    localStorage.setItem(LOCAL_STORAGE_KEY, value ? 'true' : 'false')
+  } catch (e) {
+    console.error('[setLocalStorageAiConsent] Failed to write to localStorage:', e)
+  }
+}
+
+/**
+ * Removes the persistent AI processing consent value from local storage.
+ */
+export function removeLocalStorageAiConsent(): void {
+  if (typeof window === 'undefined') return
+  try {
+    localStorage.removeItem(LOCAL_STORAGE_KEY)
+  } catch (e) {
+    console.error('[removeLocalStorageAiConsent] Failed to remove from localStorage:', e)
+  }
+}

memento-note/lib/consent/server-consent.ts

@@ -0,0 +1,30 @@
+import { auth } from '@/auth'
+import { prisma } from '@/lib/prisma'
+import { NextResponse } from 'next/server'
+
+/**
+ * Checks if the authenticated user has explicit GDPR AI processing consent.
+ * Persistent consent: UserAISettings.aiProcessingConsent
+ * Session-only consent: signed JWT claim (not client headers — GDPR-safe)
+ */
+export async function hasUserAiConsent(): Promise<boolean> {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return false
+  }
+
+  if (session.aiSessionConsent === true) {
+    return true
+  }
+
+  const settings = await prisma.userAISettings.findUnique({
+    where: { userId: session.user.id },
+    select: { aiProcessingConsent: true },
+  })
+
+  return settings?.aiProcessingConsent ?? false
+}
+
+export function aiConsentForbiddenResponse() {
+  return NextResponse.json({ error: 'ai_consent_required' }, { status: 403 })
+}