Add multiple entries per day, user management, reminders, and AI reflections

- Multiple entries per day: Home page now starts fresh, Save & New button
- Admin user management: Add/delete users, reset passwords, toggle admin
- Daily reminders: Browser notifications at configurable time
- AI reflections: Generate insights from entries using Claude API
- Remove cloud sync placeholder (already have user accounts)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/AuthProvider.tsx

@@ -7,6 +7,7 @@ interface User {
   id: string;
   email: string;
   name: string | null;
+  isAdmin: boolean;
 }
 
 interface AuthContextType {