feat: remove issues/milestones from nav, show project code

src/components/Sidebar.tsx

@@ -31,9 +31,7 @@ export default function Sidebar({ user, onLogout }: Props) {
 
   const links = user ? [
     { to: '/', icon: '📊', label: 'Dashboard' },
-    { to: '/issues', icon: '📋', label: 'Issues' },
     { to: '/projects', icon: '📁', label: 'Projects' },
-    { to: '/milestones', icon: '🏁', label: 'Milestones' },
     { to: '/notifications', icon: '🔔', label: 'Notifications' + (unreadCount > 0 ? ' (' + unreadCount + ')' : '') },
     { to: '/monitor', icon: '📡', label: 'Monitor' },
   ] : [