feat(dashboard): tableau de bord Second Brain configurable avec chargement progressif

Briefing granulaire, pistes rapides puis enrichissement async, layout persisté v5,
suggestions agents, intégration Gmail et navigation sidebar alignée sur /home.

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

memento-note/app/api/agents/suggestions/[id]/accept/route.ts

@@ -0,0 +1,21 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import { agentSuggestionService } from '@/lib/ai/services/agent-suggestion.service'
+
+export async function POST(
+  _request: NextRequest,
+  { params }: { params: Promise<{ id: string }> },
+) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  const { id } = await params
+  const result = await agentSuggestionService.accept(session.user.id, id)
+  if (!result) {
+    return NextResponse.json({ error: 'Suggestion introuvable' }, { status: 404 })
+  }
+
+  return NextResponse.json({ success: true, agentId: result.agentId })
+}