Shrink menu item text and drop the border on the account dropdown

MenuItem used text-sm (14px) for its label, which read as oversized
for a dropdown; drop to text-xs (12px). This is a shared component
(AccountMenu, ContextMenu, MobileHeader's menu), so all of them get
the more compact sizing.

Add a border prop to GlassMenu (default true, unchanged for
ContextMenu) and set it false specifically on AccountMenu's dropdown,
per feedback that its border didn't fit.

web-player/src/lib/components/ui/overlay/MenuItem.svelte

@@ -24,7 +24,7 @@
 	}: Props = $props();
 
 	const classes = $derived(
-		`flex w-full items-center gap-3 rounded-control px-2 py-2.5 text-left text-sm font-medium text-fg-2 transition hover:bg-hover ${klass}`
+		`flex w-full items-center gap-3 rounded-control px-2 py-2.5 text-left text-xs font-medium text-fg-2 transition hover:bg-hover ${klass}`
 	);
 </script>