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

apps/web/src/components/(dashboard)/layout/header.tsx

@@ -33,7 +33,7 @@ export const Header = ({ className, user, ...props }: HeaderProps) => {
   return (
     <header
       className={cn(
-        'supports-backdrop-blur:bg-background/60 bg-background/95 sticky top-0 z-[1000] flex h-16 w-full items-center border-b border-b-transparent backdrop-blur duration-200',
+        'supports-backdrop-blur:bg-background/60 bg-background/95 sticky top-0 z-[50] flex h-16 w-full items-center border-b border-b-transparent backdrop-blur duration-200',
         scrollY > 5 && 'border-b-border',
         className,
       )}