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/route.ts

@@ -0,0 +1,30 @@
+import { NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import { agentSuggestionService } from '@/lib/ai/services/agent-suggestion.service'
+
+export async function GET() {
+  const session = await auth()
+  if (!session?.user?.id) {
+    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+  }
+
+  const suggestions = await agentSuggestionService.getPending(session.user.id, 3)
+  return NextResponse.json({
+    suggestions: suggestions.map(s => ({
+      id: s.id,
+      topic: s.topic,
+      reason: s.reason,
+      suggestedType: s.suggestedType,
+      suggestedFrequency: s.suggestedFrequency,
+      relatedNoteCount: (() => {
+        try {
+          return JSON.parse(s.relatedNoteIds).length
+        } catch {
+          return 0
+        }
+      })(),
+      clusterId: s.clusterId,
+      createdAt: s.createdAt.toISOString(),
+    })),
+  })
+}