feat(desktop): redesign privacy step with single column layout

- Simplify permissions step to single centered column
- Replace per-item switches with single "I understand" checkbox
- Add capabilities info card with clean dividers
- Add trust note section for privacy messaging
- Rename step from "Permissions" to "Privacy" for clarity
- Add fade-in animation for step transitions
- Add shadcn checkbox component

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

packages/ui/src/components/ui/checkbox.tsx

@@ -0,0 +1,29 @@
+"use client"
+
+import { Checkbox as CheckboxPrimitive } from "@base-ui/react/checkbox"
+
+import { cn } from "@multica/ui/lib/utils"
+import { HugeiconsIcon } from "@hugeicons/react"
+import { Tick02Icon } from "@hugeicons/core-free-icons"
+
+function Checkbox({ className, ...props }: CheckboxPrimitive.Root.Props) {
+  return (
+    <CheckboxPrimitive.Root
+      data-slot="checkbox"
+      className={cn(
+        "border-input dark:bg-input/30 data-checked:bg-primary data-checked:text-primary-foreground dark:data-checked:bg-primary data-checked:border-primary aria-invalid:aria-checked:border-primary aria-invalid:border-destructive dark:aria-invalid:border-destructive/50 focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 flex size-4 items-center justify-center rounded-[4px] border transition-colors group-has-disabled/field:opacity-50 focus-visible:ring-3 aria-invalid:ring-3 peer relative shrink-0 outline-none after:absolute after:-inset-x-3 after:-inset-y-2 disabled:cursor-not-allowed disabled:opacity-50",
+        className
+      )}
+      {...props}
+    >
+      <CheckboxPrimitive.Indicator
+        data-slot="checkbox-indicator"
+        className="[&>svg]:size-3.5 grid place-content-center text-current transition-none"
+      >
+        <HugeiconsIcon icon={Tick02Icon} strokeWidth={2} />
+      </CheckboxPrimitive.Indicator>
+    </CheckboxPrimitive.Root>
+  )
+}
+
+export { Checkbox }