feat: add navigation link to projects in CanvasMenubar and enhance AppSidebar with tooltip for expand button

frontend/src/app/canvas/CanvasMenubar.tsx

@@ -3,6 +3,7 @@
  */
 
 import React, { useEffect } from 'react'
+import { Link } from 'react-router-dom'
 import {
   Menubar,
   MenubarContent,
@@ -17,7 +18,7 @@ import {
 } from '@/components/ui/menubar'
 import { Kbd, KbdGroup } from '@/components/ui/kbd'
 import { useTheme } from '@/lib/themeContext'
-import { Download, FolderOpen, Moon, Redo2, Sun, Undo2 } from 'lucide-react'
+import { ArrowLeft, Download, FolderOpen, Moon, Redo2, Sun, Undo2 } from 'lucide-react'
 
 export type CanvasMenubarProps = {
   onImport: () => void
@@ -72,6 +73,13 @@ export function CanvasMenubar({
 
   return (
     <Menubar className="shrink-0 rounded-none border-x-0 border-t-0 border-b-0">
+      <Link
+        to="/projects"
+        aria-label="Back to projects"
+        className="flex shrink-0 items-center rounded-sm px-2 py-1 text-sm outline-none focus:bg-accent focus:text-accent-foreground hover:bg-accent hover:text-accent-foreground"
+      >
+        <ArrowLeft className="size-4" />
+      </Link>
       <MenubarMenu>
         <MenubarTrigger className="font-medium">Project</MenubarTrigger>
         <MenubarContent>