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/lib/dashboard/home-route.ts

@@ -0,0 +1,17 @@
+/** True when /home shows the Second Brain dashboard (not list, editor, or filters). */
+export function isDashboardHomeRoute(
+  pathname: string,
+  searchParams: Pick<URLSearchParams, 'get'>,
+): boolean {
+  if (pathname !== '/home') return false
+  return (
+    searchParams.get('forceList') !== '1' &&
+    !searchParams.get('notebook') &&
+    !searchParams.get('search') &&
+    !searchParams.get('labels') &&
+    !searchParams.get('shared') &&
+    !searchParams.get('reminders') &&
+    !searchParams.get('color') &&
+    !searchParams.get('openNote')
+  )
+}