feat: Add keyboard shortcut enhancements with Kbd component

- Add shadcn kbd component for displaying keyboard shortcuts
- Enhance file manager context menu to display shortcuts with Kbd component
- Add 5 new keyboard shortcuts to file manager:
  - Ctrl+D: Download selected files
  - Ctrl+N: Create new file
  - Ctrl+Shift+N: Create new folder
  - Ctrl+U: Upload files
  - Enter: Open/run selected file
- Add keyboard shortcut hints to command palette footer
- Create helper function to parse and render keyboard shortcuts

src/components/ui/kbd.tsx

@@ -0,0 +1,28 @@
+import { cn } from "@/lib/utils"
+
+function Kbd({ className, ...props }: React.ComponentProps<"kbd">) {
+  return (
+    <kbd
+      data-slot="kbd"
+      className={cn(
+        "bg-muted text-muted-foreground pointer-events-none inline-flex h-5 w-fit min-w-5 items-center justify-center gap-1 rounded-sm px-1 font-sans text-xs font-medium select-none",
+        "[&_svg:not([class*='size-'])]:size-3",
+        "[[data-slot=tooltip-content]_&]:bg-background/20 [[data-slot=tooltip-content]_&]:text-background dark:[[data-slot=tooltip-content]_&]:bg-background/10",
+        className
+      )}
+      {...props}
+    />
+  )
+}
+
+function KbdGroup({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <kbd
+      data-slot="kbd-group"
+      className={cn("inline-flex items-center gap-1", className)}
+      {...props}
+    />
+  )
+}
+
+export { Kbd, KbdGroup }