style(console-web): use canonical Tailwind utilities

Replace the hard-coded brand text color with its theme token and use Tailwind's standard z-index utility for Host notifications.

crates/wasmeld-console/web/src/host/app.tsx

@@ -403,7 +403,7 @@ export default function HostApp() {
     <div class="grid h-dvh min-w-0 grid-cols-[minmax(0,1fr)] grid-rows-[auto_56px_minmax(0,1fr)_30px] overflow-hidden bg-canvas lg:grid-cols-[232px_minmax(0,1fr)] lg:grid-rows-[64px_minmax(0,1fr)_30px]">
       <aside class="border-line min-w-0 bg-[#16221f] text-white lg:row-span-3 lg:flex lg:min-h-0 lg:flex-col lg:border-r">
         <div class="flex h-16 shrink-0 items-center gap-3 px-4 lg:px-5">
-          <span class="flex size-9 items-center justify-center rounded-md bg-[#e5f4ef] text-[#155a46]">
+          <span class="flex size-9 items-center justify-center rounded-md bg-[#e5f4ef] text-brand-strong">
             <Boxes size={19} />
           </span>
           <div>
@@ -533,7 +533,7 @@ export default function HostApp() {
 
       <Show when={toast()}>
         {(message) => (
-          <div class="fixed bottom-12 right-5 z-[70] max-w-sm rounded-md bg-[#16221f] px-4 py-3 text-sm text-white shadow-xl">
+          <div class="fixed bottom-12 right-5 z-70 max-w-sm rounded-md bg-[#16221f] px-4 py-3 text-sm text-white shadow-xl">
             {message()}
           </div>
         )}