feat: Nova UI component library + Studio dropdown/picker polish

- Add Nova UI library: Button, TextInput, Textarea, FormField, Select,
  NovaSelect, Checkbox, Radio/RadioGroup, Toggle, DatePicker,
  DateRangePicker, Modal + barrel index.js
- Replace all native <select> in Studio with NovaSelect (StudioFilters,
  StudioToolbar, BulkActionsBar) including frosted-glass portal and
  category group headers
- Replace native checkboxes in StudioGridCard, StudioTable, UploadSidebar,
  UploadWizard, Upload/Index with custom Checkbox component
- Add nova-scrollbar CSS utility (thin 4px, semi-transparent)
- Fix portal position drift: use viewport-relative coords (no scrollY offset)
  for NovaSelect, DatePicker and DateRangePicker
- Close portals on external scroll instead of remeasuring
- Improve hover highlight visibility in NovaSelect (bg-white/[0.13])
- Move search icon to right side in NovaSelect dropdown
- Reduce Studio layout top spacing (py-6 -> pt-4 pb-8)
- Add StudioCheckbox and SquareCheckbox backward-compat shims
- Add sync.sh rsync deploy script

resources/js/components/ui/SquareCheckbox.jsx

@@ -0,0 +1,5 @@
+/**
+ * @deprecated Use the unified Checkbox from Components/ui instead.
+ * This shim exists only for backward compatibility.
+ */
+export { default } from '../ui/Checkbox'