feat(ui): redesign sidebar and fix disclaimer

- Redesign AppSidebar with collapsible groups ("Identity & Access", "System")
- Nest "Shared Data" under "Accounts" in sidebar
- Add collapsible UI component for sidebar nesting
- Fix LocalhostDisclaimer by moving it inside SidebarProvider
- Add roadmap entry for sidebar redesign

ui/package.json

@@ -17,6 +17,7 @@
   "dependencies": {
     "@hookform/resolvers": "^5.2.2",
     "@radix-ui/react-alert-dialog": "^1.1.15",
+    "@radix-ui/react-collapsible": "^1.1.12",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",
     "@radix-ui/react-label": "^2.1.8",