fix: resolve conflicting z-index values (#788)

## Description

Currently there are various z-index values that are causing:
- Toasts to be placed behind dialog blur background
- Menu being cropped off by header

## Changes Made

- Revert `z-[1000]` back to `z-50` for the header (not exactly sure why
it was bumped)
- Refactor z-indexes over 9000 to start from 1000
- Ensure z-index of toast is higher than dialog

packages/ui/primitives/dialog.tsx

@@ -20,7 +20,7 @@ const DialogPortal = ({
 }: DialogPrimitive.DialogPortalProps & { position?: 'start' | 'end' | 'center' }) => (
   <DialogPrimitive.Portal {...props}>
     <div
-      className={cn('fixed inset-0 z-[9999] flex justify-center sm:items-center', {
+      className={cn('fixed inset-0 z-[1000] flex justify-center sm:items-center', {
         'items-start': position === 'start',
         'items-end': position === 'end',
         'items-center': position === 'center',