feat(sprint-5): Phase 6 — Staff management UI (list, invite, permissions, revoke)

- /settings/staff: staff account table with role badges + permission chips
- Invite sheet: email + role template + 8 granular permission checkboxes
- Edit permissions dialog with optimistic update
- Revoke access with AlertDialog confirmation
- React Query hooks wired (useStaffListQuery, mutations)
- Full i18n (de/en), mock fallback, loading skeletons
- Sidebar nav updated: Personal → /settings/staff with UserCog icon
- Added @radix-ui/react-checkbox + Checkbox UI component

cannamanage-frontend/src/components/ui/checkbox.tsx

@@ -0,0 +1,30 @@
+"use client"
+
+import * as React from "react"
+import * as CheckboxPrimitive from "@radix-ui/react-checkbox"
+import { Check } from "lucide-react"
+
+import { cn } from "@/lib/utils"
+
+const Checkbox = React.forwardRef<
+  React.ComponentRef<typeof CheckboxPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof CheckboxPrimitive.Root>
+>(({ className, ...props }, ref) => (
+  <CheckboxPrimitive.Root
+    ref={ref}
+    className={cn(
+      "border-primary ring-offset-background focus-visible:ring-ring data-[state=checked]:bg-primary data-[state=checked]:text-primary-foreground peer h-4 w-4 shrink-0 rounded-sm border focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-offset-2 disabled:cursor-not-allowed disabled:opacity-50",
+      className
+    )}
+    {...props}
+  >
+    <CheckboxPrimitive.Indicator
+      className={cn("flex items-center justify-center text-current")}
+    >
+      <Check className="h-3.5 w-3.5" />
+    </CheckboxPrimitive.Indicator>
+  </CheckboxPrimitive.Root>
+))
+Checkbox.displayName = CheckboxPrimitive.Root.displayName
+
+export { Checkbox }